What is the explanation of Calhoun's theory of nullification?

The theory of nullification, introduced by John C. Calhoun, claims that a state in theory has the right to nullify or invalidate any federal law that the state deems unconstitutional. This theory is no longer in use today, but was a large factor in many legal cases and situations prior to and during the Civil War era.

The theory is based on the idea that the Constitution was created by an agreement or a compact between the states and would not exist without this cooperation. With this ideal, Calhoun stated that the federal law was not more influential or powerful than the individual states' laws and that the states had the last say in determining the limit of the power of the federal government.