He hasn't directly stated how, yet, but I have a relative in California that keeps saying he thinks ammunition ("bullets") should be "much, much, much tougher" for people to get.
As far as he's concerned, impossible to get
would be perfectly acceptable as a "reasonable restriction". (He was previously in favor of the 500% ammo tax, as well.)
THAT, as we all know, is the problem with ambiguous terms like "reasonable restrictions"....