My GUESS:
National laws vs State laws are two separate entities. It's illegal to use marijuana Federally, but some states make it legal.
I not comparing drug use with the firearm issue, but just illustrating states rights don't always align with Federal laws. I'm no lawyer, but I suspect the Florida firearm issue could drag on and on and o.... ......
Those of us that see the U.S. Constitution making this a cut and dried issue are likely to be frustrated.