It was mentioned in a comment already. This is nothing but a move say that they "did something" in the wake of such an event. The word appease comes to mind...
Ok, I'll play that game. My Militia's name is WoogiDeeWook. There, I'm a member of a militia. I'll even draft rules so that it's well regulated. Problem sorted. Silliness aside, that's not what "well regulated" meant at the time. Do some reading at http://bearingarms.com/well-regulated/ to catch up on its syntactical context.
Let's dumb this down a bit to adequately illustrate the legal precedent this sets. Hey the government put you on a list, in which they determined you are dangerous. No arrest, no trial, no charges. You are no longer entitled to your (enter number) Amendment Right. okthxbye