The preamble to Senator Dianne Feinstein's (D-CA) "assault weapons" banning bill describes the purpose of the proposed law as "[regulating] assault weapons, [and ensuring] that the right to keep and bear arms is not unlimited." 

The bill was introduced on Jan. 24, and was referred to the Senate Judiciary Committee.

The bill lists approximately 150 banned weapons, including "semiautomatic rifles" that "accept a detachable magazine and any 1 of the following: a pistol grip, a forward grip, a folding, telescoping, or detachable stock, or a threaded barrel" (among other things).

It bans "semiautomatic pistols" with the "capacity to accept a detachable magazine and any 1 of the following: a threaded barrel, a second pistol grip, or a barrel shroud" (among other things). 

It bans any "semiautomatic shotgun" that has a pistol grip, a folding, telescopic, or detachable stock, "the ability to accept a detachable magazine," or a forward grip (among other things).

The bill allows that banned weapons already owned before its passage to be grandfathered in but explicitly states that beginning "90 days after the date of enactment" of the bill into law, it shall be "unlawful for any person to transfer a grandfathered semiautomatic assault weapon to any" person other than a one who is licensed.

Once the bill takes effect, the supply of such weapons ends and the location of every weapon is fixed.

This is to "ensure that the right to keep and bear arms is not unlimited."