And Slave owners didn't want to hand over their slaves. They really did have God on their side too. Maybe a couple of shoot outs involving actual military level gun nuts on the receiving end of fire, would move the debate along a tad.
Most of the militias are god fearing, evolution denying, rapture enthusiastic Christians. A few objectives could be achieved here.
A reduction in the mad bastard gene pool. People being sent to their maker who they just pray to for a reunion everyday. How can that be a bad thing?
If congress pass a law and they break it, they are enemies within. Or does democracy only count when they win?
Pass the law and take them on. Trump is spending a heck of a lot on the military, give them something to kill without all the travel and language problems we encounter by invading other places. If you refuse to obey a law that prevents removing military class weapons from killing your fellow citizens and you get violent you deserve all that should be thrown at you.
Job done.