Summary

Zusammenfassung

International treaties are subject to considerable change in the course of time. The dynamics of international relations and swift social, economic and technological development on regional and global scales put these legal instruments under permanent pressure to adapt. The rise of international terrorism, the financial and debt crisis as well as the acceleration of climate change illustrate this fact. Sometimes the reaction is a new treaty, but more frequently, existing treaties have to be adapted to changing circumstances. Due to complicated formal amendment procedures demanding long negotiations, express agreement from a majority or all parties and, possibly, consent of domestic bodies, this adaptation often occurs informally. There are basically two ways of informal adaptation: interpretation and informal amendment/modification. Both ways can be implemented through the subsequent practice of the parties to the treaty. It rests upon the basic idea that it is the exclusive responsibility of the parties as creators of the treaty to dispose of its rules informally with their concordant practice of application. Article 31 (3) (b) of the Vienna Convention on the Law of Treaties (VCLT) acknowledges subsequent practice as a means of interpretation, customary internationa law recognizes practice as a basis for informal modification of a treaty.