One of the huge problems is that guns are easy to steal, hide, smuggle, and transfer with no paper trail whatsoever. The people we don't want to have access won't be bothered by the niceties of Newsome's efforts.
It's kinda the problem Chicago has. Big problems with gun violence resulted in strict gun control laws. But that only affects law abiding citizens of Chicago. Here in Indiana, which includes southern Chicago, guns are easily available. People who don't much care about the law can easily drive here, buy weapons that are illegal to buy in Chicago, and go right back up the road.
Chicago effectively disarmed law abiding folks, while Indiana kept arming criminals. We can all see the results.
Tom