This is silly.
Even if Congress were stupid enough to pass such a law, and Obama were stupid enough to sign it (okay, those two are possible), it would be brought to the Supreme Court almost immediately, suspended and struck down.
Obama has shown time and time again that he doesn't care about those petitions; they're just a way to make him look like he's in touch and accepts advice when really he just assigns one of his aides to write a condescending, ill-informed response.
If you make it to the threshold and wait six months or so for him to bother to even do that much, you'll probably get a response along the lines of "we accept that free speech is sacred but we must protect children blah blah shootings blah blah increasingly violent behaviour".
(Former) Lead Moderator and (Eternal) VGC Detective 
