The assault weapons ban was not renewed because there were not enough votes as AW are what many people lawfully defend their families and property with.
There are existing laws preventing mentally incompetent from owning / purchasing weapons.
AND THEY DON'T WORK!!!!!
This is what you guys don't seem to get. If you have a law to keep Joker Holmes from getting a gun, and he is able to walk into a gun store, Orange hair and all, doing his bad Heath Ledger impersonation, and they say, "Oh, hey, here's a semi-automatic rifle AND a 100 round drum magazine!"-
Then those laws aren't working and you come up with a law that does.
The Assault Weapons ban was not renewed because the Scumwads in the NRA have Congress' balls in a lockbox.