The Kentucky and Virginia Resolutions (or Resolves) were political statements drafted in 1798 and 1799, in which the Kentucky and Virginia legislatures took the position that the federal Alien and Sedition Acts were unconstitutional. The resolutions argued that the states had the right and the duty to declare unconstitutional acts of Congress that were not authorized by the Constitution. In doing so, they argued for states' rights and strict constructionism of the Constitution. The Kentucky and Virginia Resolutions of 1798 were written secretly by Vice President Thomas Jeffersonand James Madison respectively.

The principles stated in the resolutions became known as the "Principles of '98". Adherents argue that the states can judge the constitutionality of central government laws and decrees. The Kentucky Resolutions of 1798 argued that each individual state has the power to declare that federal laws are unconstitutional and void. The Kentucky Resolution of 1799 added that when the states determine that a law is unconstitutional, nullification by the states is the proper remedy. The Virginia Resolutions of 1798 refer to "interposition" to express the idea that the states have a right to "interpose" to prevent harm caused by unconstitutional laws. The Virginia Resolutions contemplate joint action by the states.

The Resolutions had been controversial since their passage, eliciting disapproval from ten state legislatures. Ron Chernow assessed the theoretical damage of the resolutions as "deep and lasting... a recipe for disunion".^[1] George Washington was so appalled by them that he told Patrick Henry that if "systematically and pertinaciously pursued", they would "dissolve the union or produce coercion".^[1] Their influence reverberated right up to the Civil War and beyond.^[2] In the years leading up to the Nullification Crisis, the resolutions divided Jeffersonian democrats, with states' rights proponents such as John C. Calhoun supporting the Principles of '98 and President Andrew Jackson opposing them. Years later, the passage of the Fugitive Slave Act of 1850 led anti-slavery activists to quote the Resolutions to support their calls on Northern states to nullify what they considered unconstitutional enforcement of the law