Treaties Under International and U.S. Law
One of the most important sources of international law is the formal treaties formed between or among nations. A bilateral treaty is an international agreement that has a legally binding effect on two sovereign states, while a multilateral treaty is an international agreement that has a legally binding effect on three or more states. (This definition applies even if an international agreement does not include the word “treaty.”) Sometimes a UN organ or another pre-existing international organization oversees treaty negotiations. In other cases, a treaty may be negotiated by an entity formed for that purpose.
Once representatives of the sovereign states negotiating a treaty have signed it, the treaty may become legally binding immediately. However, some treaties provide that they must be ratified by a signatory state to legally bind that state. Ratification involves formally confirming in writing that the state consents to the treaty and depositing the ratification instrument at a place provided by the treaty.
Treaties and Executive Agreements Under U.S. Law
The Supremacy Clause of the U.S. Constitution provides that treaties are part of "the supreme law of the land," similar to federal laws. This means that they may preempt conflicting state laws. An international agreement is defined as a “treaty” under U.S. law if it has received the consent of two-thirds of the Senate and has been ratified by the President. If the Senate consents to a treaty, but the President declines to ratify it, the treaty will not take effect for the U.S. This has happened several times.
Sometimes the President negotiates an international agreement but does not get the consent of two-thirds of the Senate. This is known as an executive agreement under U.S. law, although it is still considered a treaty under international law. While the Supremacy Clause does not necessarily make executive agreements "the supreme law of the land," the U.S. Supreme Court has ruled that valid executive agreements generally may preempt state laws due to the power of the federal government over foreign relations.
A provision in an international agreement may be "self-executing." This means that it automatically takes effect as enforceable federal law upon its ratification. Each provision in an agreement may be evaluated independently, meaning that some could be considered self-executing but others not.
If a provision in an international agreement is not self-executing, it is enforceable in U.S. courts only if Congress passes legislation to implement it. Until then, pre-existing federal or state law governs situations where it conflicts with the agreement. Regardless of whether a provision is enforceable in domestic courts, though, it binds the U.S. in the field of international law.
