If you're thinking of the gun free school zone law, I don't think it quite supports your point. I believe the Commerce Clause was used to justify federal regulation of gun purchases/ownership, as opposed to it having to be a state law. It was not used (I believe) in any way to abrogate the rights afforded by the Second Amendment. I could be wrong — I never practiced law in this area — but I can't remember ever hearing about the Commerce Clause being used as a limitation on the Second Amendment. That is effectively what would be required here.