Interesting since he's a prohibited person either from a felony arrest for domestic violence against Madonna, which later was convicted as a misdemeanor under the Lautenberg Amendment.
I hear some people are agitating over this fact, and pushing for an investigation/prosecution, but nobody really expects anything to come of it. But IMO I think a full-court press by several 2A groups and various right-wing concerns who ought not like him over his politics and support for Chavez and Venezuela would be a good thing. Not so much as to punish Mr. Penn, but to teach the Left in general that they might want to reconsider their usual M.O. of constantly looking for "gotchas" when it comes to people on the right or RKBA in general.