28 States don't.
Criminals don't care about laws and regulations, and guns don't have an expiration date. There are currently more guns than people now in America. The country will have to stop manufacturing guns then actively go around and seize guns to see change. Legislation doesn't fix problems over night, it'll take generations of consistent prosecution of criminals ON TOP OF gun legislation. Along with dealing with education and lack of resources in neglected communities.
In the mean time, innocent lives will be lost. This problem isn't as cut and dry as people try to make it.