The Identifi cation of Customary International Law by Austrian Courts August Reinisch and Peter Bachmayer* I. Introduction Customary international law, that venerable bedrock of inter-state law, has received increased attention recently. After the International Law Associ- ation (ILA),1 the International Law Commission (ILC) included the topic ‘Formation and evidence of customary international law’ in its programme of work,2 and subsequently decided to focus on the question of the ‘Identi- fi cation of customary international law’.3 The following contribution aims at analysing how domestic courts in Austria have addressed this issue of identifying custom. Article 38 of the Statute of the International Court of Justice (ICJ) refers to customary international law as ‘evidence of a general practice accepted as law’ and lists it as one of the main sources of international law. Custom is formed by two essential elements: (1) a consistent practice of states as indicated by a state’s external behavior towards other states as well as by internal acts like domestic legislation, government memoranda or judicial decisions if they relate to the international fi eld; and (2) the belief that such a practice has a legally binding effect upon the state (opinio iuris). * August Reinisch is Professor of International and European Law at the University of Vienna and Vice-Dean of the Law School of the University of Vienna. He may be contacted at
[email protected]. Peter Bachmayer is a project assistant with the EU-funded project ‘International Law Through the National Prism’. He may be contacted at
[email protected].