More than one year after Russia's full-scale invasion of Ukraine, hostilities continue unabated. In addition to Crimea, the Russian Federation claims sovereignty over the Ukrainian territories which it annexed in early autumn. This article scrutinizes Russia's conduct and the reaction of the international community in the light of international law. It focuses on a possible peace settlement which would affirm Russia's sovereignty over Crimea and the recently annexed territories or part of them, and argues that it would be void under Articles 52 and 53 of the 1969 Vienna Convention on the Law of Treaties.