Case Concerning the Gabcikovo-Nagymaros Project (Hungary/Slovakia)
International Court of Justice
1997 I.C.J. 7
Hungary (defendant) and then-Czechoslovakia (plaintiff) agreed by treaty in 1977 to jointly build and operate two dams on the Danube River, later abandoning the Nagymaros dam in 1992 over asserted long-term threats to marine life and requesting termination of the treaty; Czechoslovakia (soon Slovakia) rejected that termination and instead unilaterally implemented Variant C, rerouting a significant portion of the river along the border, which Hungary argued cut off water supply to its capital and further harmed aquatic life. The two nations submitted the dispute to the ICJ.
Whether a state may justify breaching an international treaty obligation on grounds of ecological necessity when alternative, less drastic means existed to address the environmental concern and the state itself contributed to creating that situation.