There are many problems with this bill, not the least of which is the fact that the scope of the Second Amendment is very much in flux. Last week, the NRA announced it would launch of blizzard of litigation intended to expand gun rights while the courts are still controlled by very conservative judges. So a lawmaker who introduces legislation that is perfectly constitutional could conceivably find that their bill suddenly violates a new understanding of the Second Amendment after the NRA wins another lawsuit — and thus could suddenly be hit with felony charges.
The biggest problem with the bill, however, is that it almost certainly violates the Missouri Constitution, which provides that “[s]enators and representatives . . . shall not be questioned for any speech or debate in either house in any other place.” Although there are very few court decisions interpreting this clause in the Missouri Constitution, the United States Constitution contains a parallel clause guaranteeing that federal lawmakers shall not be called to account for “any Speech or Debate in either House” of Congress, and courts commonly interpret parallel provisions of state and the U.S. Constitution to have similar meanings.
In United States v. Johnson the Supreme Court explained that this “Speech or Debate” clause of the Constitution is intended to prevent the “instigation of criminal charges against critical or disfavored legislators by the executive in a judicial forum” by giving them broad immunity to prosecutions for their official actions. Moreover the clause does not simply protect lawmakers engaged in literal speech or debate, but it also ensures that they will remain unmolested for actions “generally done in a session of the House by one of its members in relation to the business before it.” Thus, a lawmaker’s decision to introduce a bill for consideration by the legislature is protected by the Speech and Debate clause, and they cannot be subject to prosecution for this act.