The subject-matter of this article are the issues of treaty law as expounded in the Judgment in the Gabčíkovo-Nagymaros case. The following problems are discussed: unilateral suspension and abandonment of obligations deriving from the binding treaty; the principle of fundamental change of circumstances; unilateral termination of a treaty; applicability of the 1969 Vienna Convention on the Law of Treaties in this case; legal status of so-called ‘provisional solution’; impossibility of performance and material breach of treaty; the application of the principle of ‘approximate application’; and the principle pacta sunt servanda. The issues arc discussed at the background of the Drafts of the International Law Commission.