The Claimants (Mr. David Richard Aven, Mr. Samuel Donald Aven, Ms. Carolyn Jean Park, Mr. Eric Allan Park, Mr. Jeffrey Scott Shioleno, Mr. David Alan Janney, and Mr. Roger Raguso) – citizens of the United States of America – have brought claims against Costa Rica and submitted this dispute to arbitration pursuant to Chapter Ten of the Dominican Republic-Central America Free Trade Agreement (DR-CAFTA) and the UNCITRAL Arbitration Rules, as revised in 2010. As agreed by the Parties, the International Centre for Settlement of Investment Disputes (ICSID) serves as the administering authority for this proceeding.

This dispute arises from an investment made by the Claimants through several commercial entities established in accordance with the laws of Costa Rica which own several parcels of land comprising approximately 37 hectares on the Central Pacific Coast, as well as a concession site, that integrate a tourism project that they intended to develop to be known as "Las Olas Project". Claimants have alleged that they received in due course all requisite municipal and national government permits and approvals, including environmental viability and construction permits, and thus commenced the development of the project. Then, unexpectedly and on the basis of unsupported complaints by neighbors to the site, the Costa Rican authorities began new inspections and identified alleged wetlands and forest grounds within the project site; issued administrative and judicial actions that shut down the project. The claims were brought under Dominican Republic-Central America Free Trade Agreement. As environmental legal framework for this dispute Costa Rica relied on its 1949 Constitution, the Convention on Wetlands (Ramsar Convention), the Convention on Biological Diversity and Costa Rican environmental domestic legislation (para. 423). Claimants asserted that Costa Rica has 1) violated the fair and equitable treatment standard of DR-CAFTA Article 10.5; 2) violated the Investors’ legitimate expectation that Costa Rica would uphold the rule of law and act in accordance with its own laws and validly-issued permits; 3) breached its obligation to afford U.S. investors and their investments non-discriminatory treatment under DR-CAFTA Articles 10.3 and 10.4; 4) violated Article 10.7 DR-CAFTA by indirectly expropriating the Investors’ right to the value of their investment without compensation. The Respondent (Costa Rica) has argued that the protection of the environment is a key governmental policy, which has been acknowledged under DR-CAFTA, and that the rights of investment protection granted to investors under the Treaty may be subordinated to the protection of the environment.

The conclusions of Tribunal were concentrated over the definition of wetlands and forests, their determination within Claimants’ possessions and damage caused to environment by Claimants’ activities. The Tribunal found that under DR-CAFTA there were elements of subordination between the right of investors under Chapter Ten and the right of Costa Rica to ensure that the investments are carried out in a matter sensitive to environmental concerns (para. 412). The Tribunal concluded that Costa Rica's actions were neither arbitrary nor in breach of the DR-CAFTA. A wetland had been damaged by the Claimants' development activities and the state's measures to protect the wetland were taken in accordance with domestic laws and international law (para. 585).

Since the early 1990s many countries have included environmental language in their more recent treaties. The Tribunal’s award interpreted the example of such incorporation, DR-CAFTA. The Tribunal adjudicated the interdependence between investors’ rights in conducting their economic activities and States’ environmental policy. However, it highlighted that this does not give Costa Rica an absolute right to implement its environmental laws in arbitrary discriminatory way. This award contributes to the development of the jurisprudence regarding the interaction between a state's right to apply and enforce its environmental protection laws and the protection of investments.

Costa Rica instituted proceedings against Nicaragua before the International Court of Justice (ICJ) for incursion into, occupation of, and use by Nicaragua’s army of Costa Rica’s territory, and for causing damage to its rainforests and wetlands. Nicaragua, in turn, filed Application against Costa Rica alleging that Costa Rica violated Nicaragua’s sovereignty and caused major environmental damage on its territory due to road construction works in the border area between two countries. In 2015, ICJ rendered a decision, with the question of compensation owed by Nicaragua to Costa Rica left to be decided by agreement of the Parties, and if failed.

According to the principle of international law elaborated by the Permanent Court of International Justice (Factory at Chorzów, Jurisdiction, Judgment No. 8, 1927, P.C.I.J., Series A, No. 9, p. 21), “the breach of an engagement involves an obligation to make reparation in an adequate form”. In Pull Mills case the ICJ held that the compensation may be an appropriate form of reparation where restitution is materially impossible or unduly burdensome (Pulp Mills on the River Uruguay (Argentina v. Uruguay), Judgment, I.C.J. Reports 2010 (I), pp. 103-104, para. 273). The determination of compensation, particularly of establishment of causation, is impeded in cases of environmental damage. In this case Costa Rica claimed for two categories of compensation: for quantifiable environmental damage caused by Nicaragua’s excavation in 2010 and 2013 (eastern channel) and for costs and expenses incurred as the result of Nicaragua’s unlawful activities, including expenses incurred to monitor or remedy the environmental damage caused. Costa Rica considered “ecosystem services approach” as the most suitable for the valuation of environmental damage (para. 45). Nicaragua asserted that only material damages which are limited to damage to the property of other interests of State and are assessable in financial terms can be compensated. Nicaragua relied on “ecosystem service replacement costs” approach.

The Court took the view that damage to the environment, in particular the consequent impairment or loss of the ability of the environment to provide goods and services, and the cost of the restoration of the damaged environment, was compensable under international law (para. 42). Before assigning a monetary value to the damage to the environmental goods and services caused by Nicaragua’s wrongful activities, the Court determined the existence and extent of that damage, and whether there existed a direct and certain causal link between the damage and Nicaragua’s activities (paras 72-87). Following its valuation of the damage caused to environmental goods and services, the Court awarded Costa Rica the sum of US$120,000 for the impairment or loss of the environmental goods and services of the affected area, and the sum of US$2,708.39 for restoration measures in respect of the wetland. In addition to the compensation for environmental damage, the Court awarded Costa Rica total compensation in the amount of US$236,032.16 for costs and expenses incurred as a direct consequence of Nicaragua’s unlawful activities in the northern part of Isla Portillos, as well as US$20,150.04 in pre‑judgment interest on those costs and expenses.

This is the first case where the Court adjudicates compensation for environmental damage. The ICJ’s judgment elaborates the methodology for the valuation of environmental damage. This methodology can be useful when assessing damage caused to biodiversity or its component pertaining to a State.

Costa Rica instituted proceedings against Nicaragua before the International Court of Justice (ICJ) for incursion into, occupation of, and use by Nicaragua’s army of Costa Rica’s territory, and for causing damage to its rainforests and wetlands. Nicaragua, in turn, filed Application against Costa Rica alleging that Costa Rica violated Nicaragua’s sovereignty and caused major environmental damage on its territory due to road construction works in the border area between two countries. 

The question before the Court has its origin in the territorial dispute between Costa Rica and Nicaragua over an area abutting the easternmost stretch of the Parties’ mutual land boundary (“disputed territory”) as agreed and delimited by the 1858 Treaty of Limits, the Cleveland Award and the first and second Alexander Awards. Apart from claims of sovereignty over the disputed territory, both Parties claimed the breaches of environmental treaties (the Ramsar Convention on Wetlands, the Agreement over the Border Protected Areas between Nicaragua and Costa Rica (International System of Protected Areas for Peace [SI-A-PAZ] Agreement), the Convention on Biological Diversity and the Convention for the Conservation of the Biodiversity and Protection of the Main Wildlife Areas [Priority Wilderness Areas] in Central America) and damages caused to the territory of each other due to the dredging and artificially channeling of the San Juan River.

The ICJ found that sovereignty over the disputed territory belonged to Costa Rica and that Nicaragua’s activities there were in breach of Costa Rica’s sovereignty. Moreover, the Court adjudicated on the alleged breaches of international environmental law in connection with Nicaraguan dredging activities to improve the navigability of the Lower San Juan River. ICJ stated that in oder to fulfil its obligation to exercise due diligence in preventing significant transboundary environmental harm, a State must, before embarking on an activity having the potential adversely to affect the environment of another State, ascertain if there is a risk of significant transboundary harm, which would trigger the requirement to carry out an environmental impact assessment (EIA) (para. 104). The scope of the EIA is determined in the light of each case. If the EIA confirms that there is a risk of significant transboundary harm, the State planning to undertake the activity is required, in conformity with its due diligence obligation, to notify and consult in good faith with the potentially affected State, where that is necessary to determine the appropriate measures to prevent or mitigate that risk (para. 104). It is interesting that the Court recalled that whereas the obligation to conduct of EAI is determined by international law, the specific content of the EAI required in each case is determined by States in their domestic legislation or authorization for the project (para. 157).

Based on both Parties' experts report ICJ concluded that the Nicaraguan dredging programme planned in 2006 was not such as to give rise to a risk of significant transboundary harm, either with respect to the flow of the Colorado River or to Costa Rica’s wetland, that is why Nicaragua was not required to carry out the EIA (para. 105) and fulfil the obligation to notify and consult (para. 108). Despite recognizing the unlawfulness of dredging activities in the disputed territory, the Court did not find Nicaragua responsible for breaching substantive environmental obligations (paras 119-120). As to the Nicaragua’s claims against Costa Rica, the ICJ found that the threshold for triggering the obligation to carry out EIA of the road project was met (paras 155-156), and that in absence of emergency Costa Rica was under the obligation to conduct the EIA (para. 159), including ex ante EIA, which it failed to do (paras 161-162). Nicaragua failed to prove that the construction of the road by Costa Rica caused significant transboundary harm.

In the context of biodiversity, besides reflecting on the EIA and determination of transboundary harm, the Court also stated that Article 14 of the Convention on Biological Diversity does not create an obligation to carry out an environmental impact assessment before undertaking an activity that may have significant adverse effects on biological diversity.

On 16 February 2007, the Inter-American Commission on Human Rights received a petition lodged by eight traditional leaders on behalf of the Kaliña and Lokono peoples of the Lower Marowijne River against Suriname owing to the violation of Articles 3, 21, and 25 of the American Convention, in relation to Articles 1 and 2 of this instrument. On 28 January 2014, the Inter-American Commission on Human Rights, after an extension granted to a State by the Commission to comply with recommendations and a State’s failure to provide information on compliance with each recommendation, submitted the case to the jurisdiction of the Inter-American Court of Human Rights “owing to the need to obtain justice,” and in relation to all the facts and human rights violations described in its Merits Report. Applicable law in this case includes the American Convention on Human Rights (specifically Articles 1(1), 2, 3, 21, 23, and 25), the Environmental Planning and Assessment Act of Suriname, the Nature Protection Act 1954, and international standards for the protection of indigenous rights and biodiversity, notably under the Convention on Biological Diversity.

The case originated from a series of claims by the Kaliña and Lokono indigenous peoples regarding the State of Suriname’s failure to recognize their legal personality and their collective rights to lands, territories, and natural resources traditionally occupied and used by them. These communities objected specifically to the State’s actions, including the issuance of individual property titles to non-indigenous persons, the establishment of three nature reserves (Wia Wia, Galibi, and Wane Kreek), and granting mining concessions without prior consultation. The Kaliña and Lokono peoples argued before the Inter-American Court that Suriname had violated their rights to juridical personality, collective property, and judicial protection by failing to recognize their collective rights over their traditional territories. They also emphasized that the State did not conduct adequate consultations or obtain free, prior, and informed consent for actions impacting their ancestral territories, thereby infringing upon their rights to property and cultural integrity.

The Court found that the State had violated the rights to collective property, cultural identity and participation in public affairs of the victims, mainly by preventing their effective participation and their access to some of their traditional territory and natural resources in the Galibi and Wane Kreek Nature Reserves. The State also failed to guarantee, effectively, the traditional territory of the communities affected by the environmental degradation within the Wane Kreek Nature Reserve. All of this constituted a violation of Articles 2, 21, and 23 of the American Convention on Human Rights, in relation to Article 1(1) thereof, to the detriment of the Kaliña and Lokono peoples and their members (para. 198). The Court also determined that the State failed to ensure the effective participation, by means of a consultation process, of the Kaliña and Lokono peoples before undertaking or authorizing the exploitation of the bauxite mine within their traditional territory (para. 212). Moreover, the State was found responsible for the violation of the right to judicial protection established in Article 25 of the American Convention, in relation to Articles 1(1), 2, and 13 of this instrument due to the fact, that the judicial proceedings and the petitions filed had not been effective and that the State had not provided the public information requested by the representatives or justified the impossibility of handing it over (para. 268).

In connection with the restrictions imposed on the Kaliña and Lokono in the nature reserves, the Court emphasized that, owing to their interrelationship with nature and their ways of life, the indigenous and tribal peoples can make an important contribution to nature conservation, consequently, a State must have adequate mechanisms to guarantee the right to a dignified life and to cultural identity to the indigenous and tribal peoples in relation to the protection of the natural resources that are in their traditional territories (para. 181). The preceding is important as it supports, that recognition of and respect for the rights of indigenous peoples are compatible with nature conservation and required in relation to protected areas and other environmental measures, including climate mitigation initiatives. The Court additionally highlighted Suriname’s obligations under Articles 8(j) and 10(c) of the Convention on Biological Diversity and related decisions of the Conference of Parties, essentially reading these provisions into its interpretation of the rights of the Kaliña and Lokono peoples (paras 176-178).

Australia initiated proceedings against Japan before the International Court of Justice (ICJ), alleging that Japan’s whaling program conducted under the guise of scientific research violated its obligations under the International Convention for the Regulation of Whaling (ICRW). New Zealand intervened in the case, highlighting its own concerns about whaling in the Southern Ocean. 

The case revolved around Japan’s “ARPA II” (Japanese Whale Research Program under Special Permit in the Antarctic) which purportedly conducted scientific research whaling in the Southern Ocean. Australia contended that this program was not genuinely for scientific purposes and violated the ICRW’s moratorium on commercial whaling and the prohibition on whaling in the Southern Ocean Whale Sanctuary. Japan defended its actions, asserting that JARPA II was consistent with Article VIII of the ICRW, which allows for special permits to kill, take, and treat whales for scientific research. 

The Court concluded that JARPA II was not designed and implemented for purposes of scientific research and that its scale and methods could not be justified under the exemptions provided by Article VIII. Accordingly, Japan’s whaling activities violated its obligations under the ICRW, the main purpose of which is to provide for the proper conservation of whale stocks to make possible the orderly development of the whaling industry (para. 55). The Court ordered Japan to cease the granting of permits under JARPA II. 

The ICJ’s judgment demonstrated the importance of rigorous legal scrutiny to ensure that states adhere to the obligations set forth in international environmental treaties. The Court evaluated Japan’s JARPA II program strictly within the framework of the International Convention for the Regulation of Whaling (ICRW), particularly Article VIII, which allows for scientific research, which may pursue an aim other than either conservation or sustainable exploitation of whale stocks (para. 56). Despite this, the Court found that the program’s design, scale, and implementation were inconsistent with the requirements of scientific research under the treaty and therefore violated the ICRW’s moratorium on commercial whaling and the Southern Ocean Whale Sanctuary (para. 231). While the ICJ’s reasoning was confined to the ICRW’s treaty framework, the case highlights how specific conservation measures — such as the moratorium and whale sanctuaries — reflect the treaty’s objectives to ensure the sustainable management and protection of whale populations. 

In 2006 Argentina filed an application against Uruguay to the International Court of Justice (ICJ) concerning alleged violations under Statute of the River Uruguay (1975).

The Statute of the River Uruguay (1975 Statute) was signed for the purpose of establishing the joint machinery necessary for the optimum and rational utilization of that part of the river which constitutes their joint boundary. Also, under the 1975 Statute the Administrative Commission of the River Uruguay (CARU) was established to provide joint management of the river. Before planning any activities that might affect the condition of the river, Parties should notify CARU and each other to discuss such projects prior to their approval. In the period from 2003 to 2005, two companies (ENCE and Botnia) received permission from the Uruguayan government to build pulp mills on the Uruguay River in the Fray Bentos area, without prior notification of Argentina. This unilateral decision of Uruguay entitled such consequences as partial traffic blockade, environmental protests and straining of the diplomatic relations between countries. Nevertheless, Uruguay didn’t suspend construction works of the pulp mills for more than 3 days. On 4 May 2006 Argentina filed an application to the ICJ, in which charged Uruguay for failing the obligations for optimum and rational utilization of the river (article 1 of the 1975 Statute) and for prior notification and consultation procedures under 1975 Statute (articles 7 and 13).

Argentina claimed that authorization for construction of the pulp mills were: 1) planned with violation of 1975 Statute (procedural obligation to notify and consult were failed); 2) posing a threat to the river and its environment and were likely to impair the quality of the river’s waters, therefore will cause significant transboundary damage to Argentina (substantive obligations). With the application, Argentina requested provisional measures for the Court to order Uruguay: 1) to suspend the authorizations for construction of the mills; 2) to co-operate with Argentina on the protection and conservation of the aquatic environment of the River Uruguay; and 3) to refrain from taking any further unilateral action with respect to the construction of the two mills. In return, Uruguay submitted a Request for the indication of provisional measures on the ground of the blockade held by the Argentina’s citizens on the main traffic routes over the River Uruguay. Both of the Requests for provisional measures were rejected — the Court found that the circumstances, as they then presented themselves to it, were not such as to require the exercise of its power under Article 41 of the Statute.

On 20 April 2010, Court noted in its Judgment that Uruguay violated procedural obligations under 1975 Statute by not informing CARU of the planned works before the issuing of the initial environmental authorizations for each of the mills and for the port terminal adjacent to the Orion (Botnia) mill, and by failing to notify the plans to Argentina through CARU. As for the substantive obligations, Court found no conclusive evidences that the industrial activities authorized by Uruguay had had, or would have, an adverse impact on the quality of the waters of the river and the area affected by it, and caused significant damage to the quality of the waters and significant transboundary damage to Argentina.

A separate section in the Judgment is dedicated to biodiversity (section (d) Effect on biodiversity, paras 260-262) which includes Argentina’s claims that the treaty obligation to “protect and preserve the aquatic environment” comprises an obligation to protect the biological diversity, so the activities made under 1975 Statute should comply with the obligations derived from the CITES, Biodiversity and Ramsar Conventions, which Uruguay failed to comply (para. 260). In return, Uruguay stated that Esteros de Farrapos was not included in the list of Ramsar sites which makes Ramsar Convention non-applicable in this case. Moreover, Argentina failed to provide evidences of the Biodiversity Convention breach because the dilution of the effluent from the mill would render the effluent quite harmless and below any concentration capable of constituting pollution (para. 261). The Court stated that under 1975 Statute parties have obligation to protect flora and fauna of the river, which also should reflect their international undertakings in respect of biodiversity and habitat protection (para. 262). However, Court didn’t find any sufficient evidences that Uruguay breached its obligation to preserve the aquatic environment including the protection of its fauna and flora (para. 262).

In 2000 the Association of Saramaka Authorities (ASA) and twelve Saramaka captains on their own behalf as well as on behalf of the Saramaka people of the Upper Suriname River presented a petition against Suriname state to the Inter-American Commission on Human Rights. In 2006, the Commission concluded that “the matter had not been settled” and submitted the case to the Inter-American Court of Human Rights (IACtHR). The Inter-American Court of Human Rights (IACtHR) is the principal judicial organ of the Organization of American States, competent to issue binding judgments on alleged violations of the American Convention on Human Rights (1969, ACHR). The Court considered Article 1 (1), which establishes obligation to respect rights, Article 2 (Domestic Legal Effects) in conjunction with Article 3 (Right to Juridical Personality), Article 21 (Right to Property), and Article 25 (Right to Judicial Protection).

Saramaka people are a tribal community, brought to Suriname state during the colonization period and nowadays living in the Upper Suriname River region. Their way of life is based on collective land use, hunting, fishing, gathering, traditional medicine and rituals closely linked to the forest ecosystem. Between 1997 and 2004, the State granted at least four logging concessions in the territory claimed by the Saramaka people. Also, an unspecified number of concessions were granted for gold mining. Some of these concessions were granted to individuals who are not members of the Saramaka people and others to members of the Saramaka people. According to the head captains of Saramaka people, the activities, made under granted concessions within traditional Saramaka territory, were highly destructive and caused massive damage to a substantial area of the Saramaka people’s forest and the ecological and cultural functions of the area. Therefore, the representatives asked the Court to declare that the State had violated the same rights alleged by the Commission (Articles 1(1), 21 and 25), and additionally alleged that the State had violated Article 3 (Right to Juridical Personality) of the Convention by “failing to recognize the legal personality of the Saramaka people”. Additionally, they requested certain measures of reparation and the reimbursement of the costs and expenses incurred in processing the case at the national level and before the international proceedings. In turn, representatives of the Suriname state claimed, that, firstly, it is not responsible for the violation of the right to property established in Article 21 of the Convention, because the State does recognize the Saramaka community a privilege to the land it has traditionally occupied and used; secondly, the right to judicial protection (Article 25) has not been violated, because the Surinamese legislation does provide effective legal recourse, and the State has complied with its obligation under Article 1 and Article 2 of the Convention and therefore not violated these rights. Moreover, the concessions were granted lawfully, because according to the Article 41 of the Constitution of Suriname and Article 2 of its 1986 Mining Decree, ownership rights of all natural resources vest in the State.

Even though the Saramaka people are not “indigenous” in the strict sense, the Court found that their livelihoods, historical, cultural roots, integral regulation and economic dependence on the lands make them a “tribal people” and therefore require similar protections under international law. The Court ruled that State violated (in conjunction with Article 1 (1) and 2 ACHR) the right to property (Article 21 ACHR); the right to juridical personality (Article 3 ACHR) in relation to the right to property recognized in Article 21 of such instrument and the right to judicial protection under Article 25 thereof; the right to judicial protection (Article 25 ACHR) in conjunction with the obligations to respect and guarantee the rights established under Articles 21. It ordered Suriname to delimit, demarcate and grant legal title to the Saramaka territory; adopt domestic legislation recognising indigenous land rights; ensure that any future logging, mining or infrastructure projects proceed only after (i) effective consultations in good faith with the Saramaka through culturally appropriate procedures, (ii) free, prior and informed consent whenever large-scale activities may have a major impact, (iii) prior independent and participatory environmental and social impact assessments, and (iv) equitable sharing of benefits. The Court also mandated a development fund, publication of the judgment, and reimbursement of costs.

The issue of biodiversity was not directly considered by the court, however, it was indirectly touched upon. Firstly, in the judgment, The Court explained that the physical and cultural survival of a people depends on sustainable access to land and its natural resources (paras 118-123), thus, if actions that disrupt the balance of the ecosystem occur on the territory of indigenous people, this harms indigenous people (paras 127-129). The court considers damage made under logging and gold mining concessions granted by the Suriname to third parties to be such actions (paras 144-146, 155-157). Secondly, the Court provided legal test for the restriction of aforementioned rights (by granting concessions) to be lawful and non-harming for the indigenous people in general and therefore the ecosystem they live in.

Following the Panel’s ruling, the United States appealed aspects of the decision. The Appellate Body examined the U.S. import prohibition on shrimp and shrimp products under US Law, focusing on its compatibility with the General Agreement on Tariffs and Trade (GATT) 1994 and its environmental justifications.

The dispute arose from the U.S. requirement that imported shrimp be harvested using turtle excluder devices (TEDs) to protect endangered sea turtles. The measure had already been found to violate GATT obligations by the Panel, which cited its discriminatory and inflexible application. The United States appealed this conclusion, arguing that the measure was a legitimate environmental protection policy and should be justified under Article XX(g) since the measure was necessary for the conservation of endangered sea turtles, an exhaustible natural resource.

The Appellate Body upheld the Panel’s conclusion that the U.S. measure violated Article XI:1 of GATT. However, it overturned certain findings of the Panel related to Article XX(g), ruling that the U.S. measure did qualify as one for the conservation of an exhaustible natural resource. Despite this, the Appellate Body found that the measure failed to meet the requirements of the Article XX chapeau because it resulted in unjustifiable discrimination. Specifically, the unilateral implementation of the measure without serious efforts to negotiate with the complainants or accommodate their conditions was deemed incompatible with the chapeau.

The Appellate Body recognized the legitimacy of environmental conservation under Article XX(g), marking an important step in integrating environmental concerns within the framework of WTO law. It emphasized the principle of sustainable development, requiring a balance between trade obligations and environmental protection. Moreover, Appellate Body cited Convention on Biological Diversity (paras 130, 168) and Convention on International Trade in Endangered Species of Wild Fauna and Flora (“CITES”) (paras 132, 168). This case set a precedent for considering biodiversity conservation as a legitimate objective under international trade law. It also highlighted the importance of multilateral cooperation and non-discrimination in implementing environmental measures, reinforcing the need for inclusive approaches to global biodiversity governance.

NB: The Appellate Body’s report built on the Panel’s findings, further developing WTO jurisprudence on the relationship between trade and environmental policies.

Hungary and Slovakia jointly referred a dispute to the International Court of Justice (ICJ) concerning the Gabčíkovo-Nagymaros Project. The project, governed by the 1977 Budapest Treaty between Hungary and Czechoslovakia, outlined the construction of a system of dams on the Danube River to improve navigation, generate hydroelectric power, and manage flooding. However, political changes (such as the disintegration of Czechoslovakia), economic challenges, and environmental concerns, including activism to protect the Danube River, disrupted the project. Initially frozen by mutual agreement, construction was later unilaterally suspended by Hungary.

In 1992, Hungary sought to terminate the 1977 Treaty, prompting the dispute’s submission to the ICJ. Parties submitted following questions to the Court: a) whether the Republic of Hungary was entitled to suspend and subsequently abandon, in 1989, the works on the Nagymaros project and on that part of the Gabčíkovo project for which the Treaty attributed responsibility to the Republic of Hungary; (b) whether the Czech and Slovak Federal Republic was entitled to proceed, in November 1991, to the “provisional solution” and to put into operation from October 1992 this system (the damming up of the Danube at river kilometre 1,851.7 on Czechoslovak territory and the resulting consequences for the water and navigation course); and (c) what were the legal effects of the notification, on 19 May 1992, of the termination of the Treaty by the Republic of Hungary.

In its Judgment of 25 September 1997, the Court asserted that Hungary was not entitled to suspend and subsequently abandon, in 1989, the works on the Nagymaros project and on the part of the Gabčíkovo project for which it was responsible, and that Czechoslovakia was entitled to proceed, in November 1991, to the “provisional solution” as described by the terms of the Special Agreement. On the other hand, the Court stated that Czechoslovakia was not entitled to put into operation, from October 1992, the barrage system in question and that Slovakia, as successor to Czechoslovakia, had become Party to the Treaty of 16 September 1977 as from 1 January 1993. The Court also decided that Hungary and Slovakia must negotiate in good faith in the light of the prevailing situation and must take all necessary measures to ensure the achievement of the objectives of the said Treaty, in accordance with such modalities as they might agree upon. Further, Hungary was to compensate Slovakia for the damage sustained by Czechoslovakia and by Slovakia on account of the suspension and abandonment by Hungary of works for which it was responsible, whereas, again according to the Judgment of the Court, Slovakia was to compensate Hungary for the damage it had sustained on account of the putting into operation of the dam by Czechoslovakia and its maintenance in service by Slovakia. 

The Court's Judgment established several significant principles regarding environmental obligations in international law. While acknowledging Hungary’s concerns about its natural environment to be an “essential interest”, the ICJ ruled that these environmental risks did not constitute a “state of necessity” warranting unilateral suspension of the treaty (para. 53). Significantly, the Court emphasized the ongoing need for states to assess and monitor environmental effects throughout a project’s lifecycle, as part of their obligation to prevent harm to the environment (paras 56, 112). The ICJ acknowledged the evolution of international environmental norms, emphasizing the need for states to consider new standards and the principle of sustainable development when pursuing or continuing activities that impact the environment (para. 140). Additionally, the judgment highlighted the interconnection between treaty law, environmental governance, and international cooperation, urging states to balance their obligations under existing agreements with the imperative to protect shared natural resources through collaborative efforts (paras 112, 144, 147). 

The General Assembly of the United Nations in its Resolution 49/75 K adopted on 15 December 1994 requested for the Advisory Opinion of the International Court of Justice. The question upon which the advisory opinion was requested was the following: “Is the threat or use of nuclear weapons in any circumstance permitted under international law?”

On 8 July 1996, the Court rendered its Advisory Opinion. Having concluded that it had jurisdiction to render an opinion on the question put to it and that there was no compelling reason to exercise its discretion not to render an opinion, the Court found that the most directly relevant applicable law was that relating to the use of force, as enshrined in the United Nations Charter, and the law applicable in armed conflict, together with any specific treaties on nuclear weapons that the Court might find relevant. Considering the question of the legality or illegality of the use of nuclear weapons in the light of the provisions of the UN Charter relating to the threat or use of force, the Court observed that those provisions applied to any use of force, regardless of the weapons employed (paras 38-39). In addition, it stated that the principle of proportionality might not in itself exclude the use of nuclear weapons in self-defence in all circumstances (para. 42). At the same time, a use of force that was proportionate under the law of self-defence had, in order to be lawful, to meet the requirements of the law applicable in armed conflict, including, in particular, the principles and rules of humanitarian law (para. 42). The Court pointed out that the notions of a “threat” and “use” of force within the meaning of Article 2, paragraph 4, of the Charter stood together in the sense that if the use of force itself in a given case was illegal — for whatever reason — the threat to use such force would likewise be illegal (para. 47).

The Court then turned to the law applicable in situations of armed conflict. From a consideration of customary and conventional law, it concluded that the use of nuclear weapons could not be seen as specifically prohibited on the basis of that law (paras 63, 73-74), nor did it find any specific prohibition of the use of nuclear weapons in the treaties that expressly prohibited the use of certain weapons of mass destruction. After ascertaining the applicable principles and rules of humanitarian law, the Court concluded that “in view of the current state of international law and of the elements of fact at its disposal, [it] cannot conclude definitively whether the threat or use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defence, in which the very survival of a State would be at stake” (para. 97). The Court added, lastly, that there was an obligation to pursue in good faith and to conclude negotiations leading to nuclear disarmament in all its aspects under strict and effective international control.

Though the Court did not refer to biodiversity in its reasoning, it observed that “States must take environmental considerations into account when assessing what is necessary and proportionate in the pursuit of legitimate military objectives. Respect for the environment is one of the elements that go to assessing whether an action is in conformity with the principles of necessity and proportionality” (para. 30). The environment is under daily threat and that the use of nuclear weapons could constitute a catastrophe for the environment (para. 29). The Court also recognized that “the environment is not an abstraction but represents the living space, the quality of life and the very health of human beings, including generations unborn” (para. 29).