The supreme law of the land in the United States is the Constitution. The Constitution is the source of all government powers and provides important limitations on the government that protect the fundamental rights of United States citizens. All laws in the United States must follow the Constitution. The Constitution is also the basis for the relationship between the states, requiring them to give "full faith and credit" to the laws, records, contracts, and judicial proceedings of the other states. The Constitution establishes the authority of the United States and provides important limitations on the government that protect the fundamental rights of United States citizens. The Constitution is considered the supreme law of the land because it is the highest law in the United States and all other laws must be in accordance with it.