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 California, as in all states, constitutional law primarily refers to the interpretation and application of the U.S. Constitution, which is the supreme law of the land. The Constitution takes precedence over state laws in areas where the federal government has been granted authority. It 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. Additionally, the Constitution delineates the relationships between the states, between states and the federal government, and between individuals and both levels of government. The Constitution can be amended according to the process outlined in Article V, with the first ten amendments known as the Bill of Rights. While constitutional law can also pertain to state constitutions, unless specified, it generally refers to the U.S. Constitution. In cases where state laws or actions are challenged as unconstitutional, both state and federal courts in California may interpret constitutional issues, with the possibility of appeals reaching the U.S. Supreme Court.