Interposition also involves a declaration that a federal law is unconstitutional. There are various actions that a state might take to "interpose" once it has determined that a federal law is unconstitutional. In the Virginia Resolutions of 1798, Madison did not describe the form or effect of interposition. But two years later in the Report of 1800, Madison described a variety of actions that states might take to "interpose": communicating with other states about the unconstitutional federal law, attempting to enlist the support of other states, petitioning Congress to repeal the law, introducing Constitutional amendments in Congress, or calling a constitutional convention. Madison did not argue that a state could "interpose" by legally nullifying a federal law and declaring it unenforceable. Madison contemplated that interposition would be a joint action by a number of states, not an action by a single state. Interposition is considered to be less extreme than nullification because it does not involve a state's unilateral decision to prevent enforcement of federal law.
