Tribunals (or courts) adjudicate disputes between two or more parties by applying laws and/or equity. They declare the legal obligations (if any) existing between the parties, sometimes issue reasoned opinions, and order remedies if such obligations are breached. Some tribunals need not even have an actual dispute to adjudicate to provide a declaration of the law. For example, some courts issue advisory opinions.

Sometimes constitutions, basic law, or statutes create tribunals. Sometimes, personal sovereigns or communities create tribunals. Most importantly, treaties also can create tribunals. For example, the American Convention on Human Rights created the Inter-American Court of Human Rights, and the U.S. Constitution created the Supreme Court. Sometimes an institution operating under the authority of its constituent treaty creates a tribunal. For example, the UN Security Council operating under the authority of the UN Charter created the International Criminal Tribunal for the former Yugoslavia, and Congress operating under the authority of the Constitution created the federal appellate and district courts.

Because treaties are agreements between two or more states, the tribunals established by these treaties can have jurisdiction over interstate disputes and operate as interstate tribunals. For example, the International Court of Justice (ICJ) sometimes exercises jurisdiction over disputes between states, and the U.S. Constitution gives the Supreme Court jurisdiction over interstate disputes. Given that the Constitution is a treaty between states governing their relations, it should come as no surprise that the federal courts created by the Constitution have an interstate dimension.