After the Adams Administration signed into law the Alien and Sedition Acts making it illegal to criticize the government, the Jeffersonian Republicans were forced to respond the only way they could. With Congress and the courts under the control of Federalists, Jefferson and Madison wrote the Virginia and Kentucky Resolutions. They said the new laws were in direct violation of the 1st Amendment and when Congress goes against the Constitution that the states must act. It was the states that gave the government its power when they ratified the Constitution, so if the government does something that hurts a state, the state has the power to nullify the law.
Historically Speaking 