foreign relations law: an overview
Foreign relations law of the United States encompasses both International Law, which embodies the rules that determine the rights and obligations of states and international organizations, and that part of the domestic law of the United States that involves matters of significant concern to the foreign relations of the United States.
The domestic portion of foreign relations law primarily consists of federal law: The President is empowered under the Constitution to nominate and (upon the Senate's approval) appoint ambassadors and other public ministers and consuls. These representatives are then capable of acting with binding authority.
Consuls are the main diplomatic relations vehicle for the United States. A consul is an officer commissioned by a government to represent it in a foreign country with the goal of protecting and promoting the interests of its citizens.
The states are not sovereign "states" under international law, since the Constitution does not vest them with a capacity to conduct foreign relations. They are specifically prohibited from entering into any treaty, alliance, or confederation (see Article 1, § 10). They may, however, prescribe and enforce rules of law having an effect on foreign relations unless the Constitution vests exclusive jurisdiction in the Federal Government and Congress has acted to occupy the field. For example, many foreign nationals who are present in the United states are subject to state law in ways that can have important consequences for U.S. foreign relations.
The rules of international law do not cover all aspects of the relations between the states. International Law overlaps with the Foreign Relations Law to the extent that the domestic law of the United States includes rules giving effect to rules of international law, but does not cover the same subject matter. There are many areas in which law of the United States determines the conduct of its foreign relations without reference to any international rule.