John Donohue, a Stanford law professor and gun policy expert who supported the act’s renewal, said it provides a regulatory measure to deter gun companies from purposely advancing weapons and technology aiming to bypass detectors.

“The ramifications for broad illegality are small, but the ramifications for the areas we do go through metal detectors — stadiums, courthouses, and planes — is huge,” Donohue said. “You can open yourself up to a hijacking problem pretty quickly.”