"It will ban the sale, the transfer, the importation and the possession, not retroactively, but prospectively," and ban the sale of clips of more than ten bullets, Feinstein said. The "not retroactively" wording would seem to imply that firearms already in private hands would not be subject to the new restrictions.
In a press conference last Friday with Senator Richard Blumenthal (D-CT), however, she painted a far different picture. She explains that all existing "assault weapons" would be--just as machine guns are currently--put under National Firearms Act (NFA) regulation, with all the legal hoops such regulation entails.
The guns would be registered (presumably, like machine guns, subject to periodic inspections by the Bureau of Alcohol, Tobacco, Firearms and Explosives); owners would be subject to invasive background checks, presumably fingerprinting, etc. She did not mention the $200 tax stamp for every transfer (and would that also apply to magazines--each magazine?), but if they are to be regulated "like machine guns," that would be part of it. And ownership of the gun would apparently be contingent on a local judge or chief law enforcement officer approving that ownership--with the official in question not required to provide that approval, or even a reason for disapproval.
Failure to meet any of these requirements would be grounds for confiscation.