Constitutional law is generally the interpretation and application of the United States Constitution, which is the supreme law of the land, and supersedes (preempts) all state laws on matters in which the U.S. Constitution grants the federal government authority. The Constitution is the foundation of the U.S. legal system, and defines (enumerates) the powers of the three branches of government (legislative, executive, and judicial) and each branch’s oversight of the others. The Constitution also defines the relationships between states; between states and the federal government; and between individuals and the state and federal governments.

The Constitution may be amended as provided by Article V, and the first ten amendments were ratified by the states in 1791 and are known as the Bill of Rights.

Constitutional law may also be a reference to state constitutions, but when not specifically indicated, it is considered a reference to the U.S. Constitution.

In Oklahoma, as in all states, constitutional law refers to the interpretation and application of the U.S. Constitution, which is the supreme law of the land. This means that federal law, as derived from the Constitution, preempts state laws when there is a conflict in areas where the federal government has been granted authority. The Constitution outlines the powers and functions of the three branches of the federal government—legislative, executive, and judicial—and establishes a system of checks and balances among them. It also delineates the relationships between the states, between states and the federal government, and between individuals and both levels of government. Amendments to the Constitution are possible through the process outlined in Article V, with the first ten amendments known as the Bill of Rights. While Oklahoma has its own state constitution, which governs the state's laws and government, it must comply with the U.S. Constitution. When the term 'constitutional law' is used without specification, it typically refers to the U.S. Constitution.