The International Law Commission's Guiding Principles for Unilateral Declarations and its Guide to Practice on Reservations to Treaties are among the recent developments in international law. These developments support a new assessment on how optional clauses (eg Article 62(1) of the American Convention on Human Rights) and especially the Optional Clause (Article 36(2) of the Statute of the International Court of Justice (ICJ)) can be characterised and treated. The question is in how far optional clauses and the respective declarations can be considered a multilateral treaty or a bundle of...