The answer for this would be the United Nations. When international law is violated the United Nations have a tribunal to determine the laws broken and the guilt of the accused.
The United Nations is an intergovernmental organization whose main goal is to maintain the international peace and security over nations of all around the world by seeking the cooperation and friendly relationship between them. This organization is the largest of its kind in the world and with 193 members nowadays.
The UN's principal judicial organ is the <em>International Court of Justice</em>, whose primary purpose are to <em>settle international disputes</em> and <em>to give advices about legal issues</em>. It also works as a source of international law.