The Republican-controlled House and Senate in Missouri have passed versions of a law that would nullify federal gun regulations in the state (the House vote was 110-41). Fortunately, it's a tempest in a teapot, akin to the federal House passing (yet again) a bill that would repeal Obamacare: the Democratic governor, Jay Nixon, vetoed a similar bill a year ago.
Nullification is an interesting concept. According to the Wikipedia entry for nullification:
Nullification, in United States constitutional history, is a legal theory that a state has the right to nullify, or invalidate, any federal law which that state has deemed unconstitutional. The theory of nullification has been rejected repeatedly and rarely legally upheld by the Federal courts.
The theory of nullification is based on a view that the States formed the Union by an agreement (or "compact") among the States, and that as creators of the federal government, the States have the final authority to determine the limits of the power of that government. Under this, the compact theory, the States and not the federal courts are the ultimate interpreters of the extent of the federal government's power. Under this theory, the States therefore may reject, or nullify, federal laws that the States believe are beyond the federal government's constitutional powers. The related idea of interposition is a theory that a state has the right and the duty to "interpose" itself when the federal government enacts laws that the state believes to be unconstitutional. Thomas Jefferson and James Madison set forth the theories of nullification and interposition in the Kentucky and Virginia Resolutions in 1798. A more extreme assertion of state sovereignty is the related action of secession, by which a state terminates its political affiliation with the Union.
Courts at the state and federal level have generally rejected the constitutionality of nullification, including the Supreme Court. The courts have decided that under the Supremacy Clause of the Constitution, federal law is superior to state law, and that under Article III of the Constitution, the federal judiciary has the final power to interpret the Constitution. Therefore, according to the Supreme Court's interpretation of the Supremacy Clause, the power to make final decisions about the constitutionality of federal laws lies with the federal courts, not the states, and the states do not have the power to nullify federal laws.Amato's article says:
The bill, sponsored by Rep. Doug Funderburk, R-St. Peters, allows residents to sue federal agents for enforcing past, present and future federal gun laws. It also would allow conceal carry permit holders to carry firearms openly, even in municipalities with ordinances banning this act. It would lower the minimum age to obtain a concealed carry permit to 19 from 21. School districts could designate school protection officers to carry firearms. Those volunteers would receive the same training as a police officer.