and a password could limit the risk of guns being fired by excluded people, such as felons and the mentally ill.
these identity devices may be attached to the trigger, or to the box in which a gun is stored. the fingerprint reader would be set up by law enforcement so that only the licensee could open it.
the strict constructionist right admits that the freedom to bear arms has a limit.
"Although we do not undertake an exhaustive historical analysis today of the full scope of the Second Amendment, nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms." - Scalia.
the only question is how to make the exclusion work in reality.
the idea of an identity tool does not contravene the second amendment, far as I can see.
this might solve a part of the problem.