In 2001 the International Law Commission completed its work on State responsibility, begun 40 years previously. The Articles on Responsibility of States for Internationally Wrongful Acts marks a major step in the codification and progressive development of international law, comparable in significance to the Vienna Convention on the Law of Treaties. The Articles cover such topics as attributing conduct to the State; defining when there has been a breach of international law and the excuses or justifications for breaches; reparation for injustices, the invocation of responsibility, especially standing of States in the public interest, and the rules relating to countermeasures. The Articles develop basic concepts of international law, in particular peremptory norms and obligations to the international community as a whole. They signal definitively how international law has moved away from a purely bilateral conception of responsibility to accommodate categories of general public interest (human rights, the environment etc.).