States cooperate in making and applying international law in circumstances where they are agreed upon the goals to be pursued, so that the law is employed to express a willing cooperation between them rather than to force rules upon them. ‘What international law does well’ considers the mechanisms of why and how States cooperate. Some arrangements are designed to facilitate transactions rather than to prescribe rules or standards. Examples include cooperation between legal systems and the United Nations. Key areas where international law has had success are in the international economy, through the World Trade Organization; humanitarian law and human rights; environmental protection; and the repression of criminal activity.