Federal law is the body of law created by the federal government of a country. A federal government is formed when a group of political units, such as states or provinces join together in a federation, surrendering their individual sovereignty and many powers to the central government while retaining or reserving other limited powers. As a result, two or more levels of government exist within an established geographic territory. The body of law of the common central government is the federal law.
Examples of federal governments include those of Australia, Brazil, Canada, Germany, Malaysia, Pakistan, Republic of India, Russia, the former Soviet Union and the United States.
Federal law Wikipedia
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. Issues that arise under any legislation passed by Congress, an Executive Order of the President, or a decision of federal courts pursuant to the Constitution are governed by federal law.
The Supreme Court makes final decisions regarding federal laws that they choose to hear cases about. United States federal laws are codified in the United States Code.