As I recall there was some question about Interstate Commerce. The way the laws were introduced, through regulation of Interstate Commerce were being tested. There was some thought you COULD manufacture to sell just about anything as long it was only for use inside the state of manufacture. IIRC they seriously screwed with someone who was doing this and IIRC he won.
I think the government has been hesitant to charge many gun crimes because virtually all gun laws are infringements of the Second Amendment. It only takes a few cases to turn things around.
The DC law requiring guns to be locked up at home gave us the Heller Decision. The Chicago law against handguns at home gave us the McDonald Decision. More recently the Massachusetts law against stun guns gave us the Caetano Decision.
That is only three Supreme Court decisions and the effect has been to significantly change the legal environment for gun owners. One or two more decisions by the SCOTUS and we will begin to see dramatic changes here in the People's Republik of Kalifornia.