Common sense gun laws

From Munchkin Wrangler:

MA has extremely restrictive gun laws that can land people in hot water very quickly. If I go to MA and forget a box of range ammo in my van–or even just fired brass for reloading–I am looking at three years in a MA state prison if said state trooper pulls me over, goes through the van with a very fine comb (because HEY, GUN NUT), and finds so much as a single piece of expended brass.

I'm trying to figure out how a group of legislators decides that empty brass is a dangerous object that needs to be banned or restricted.