International law becomes part of the UnitedStates law in four ways - the manner in which courts interpret statutes, by legislative reference to international law, through the use of international law principles to fill gaps in common law, andthrough the direct incorporation of treaties into the law of the land.
First, as a rule, courts of the United States interpret statutes in such a way as to comply with the nation's internationalobligations, a principle known as the Rule of Interpretation. Since the role of the court is to determine the intent of the legislature when the court interprets a statute, and the recognized generalpublic policy is to conform with international legal obligations, the court will interpret statutes to conform with international law.
Second, statutes may directly refer to international law, therebyincorporating their terms, referred to as "incorporation by reference." If a U.S. statute refers to specific treaty provisions, these specific terms are thereby given the same force as the statute.Third, international law sometimes comes into the U.S. courtroom as common law. Common law is comprised of judge-made rules subject to limits of previous court decisions and always subject tomodification by a later statute. When a court can find no other domestic law addressing an issue, then it may choose to apply international law.
Finally, the U.S. Constitution provides for the directincorporation of treaties into US law. The Treaty Supremacy Clause of the Constitution, Article VI, states, "This Constitution, and the Laws of the United States which shall be made in Pursuance thereof;...