The Missouri legislation is one of the boldest examples yet of what has become a nationwide movement among states to nullify or ignore federal laws with which local officials disagree.
U.S. District Judge Audrey Fleissig cited a provision in the U.S. Constitution declaring that federal laws take precedence over contradictory state laws.
The bill would declare any federal, state or local laws prohibiting guns to be in violation of the U.S. and Missouri constitutions, rendering them invalid.
On Wednesday, the American Civil Liberties Union filed suit over a section that says the religious rights of inmates are limited to federal law.
The measure on the statewide ballot said people have the right to pray in public or private so long as they do not disturb the peace, and it gives a specific imprimatur for prayer before government meetings.
Wedge issues are deliberately divisive measures to identify for voters a clear difference between the two political parties.
The measure would forbid companies from turning people down for jobs or treating them differently because they have a concealed carry permit or have used a firearm in the past.