The United States Constitution provides for a federal government that is superior to state governments with regard to its enumerated powers. These powers include the authority to govern international affairs, interstate commerce, the currency and national defense. After the American Civil War, the Fourteenth Amendment applied the Constitution's Bill of Rights to state governments. Legislation passed by Congress, an Executive Order of the President, or a decision of federal courts pursuant to the Constitution are federal law.
Through the system of checks and balances, it is the Supreme Court that makes final decisions regarding federal laws regarding specific cases brought before them. United States federal laws are codified in the United States Code.