I can think of several lines of approach...I'll mention some of them now.
The PBJ business gets attacked as ex post facto law.
The mental health issues get attacked as an arbitrary deprivation of civil rights without due process.
Licensing gets attacked on the grounds that it is effectively a poll tax. This is especially true if you live outside the I-95 axis. There aren't that many places that do fingerprinting in Southern Maryland, Western Maryland, or the Eastern Shore. You get to take a half-day off of your job to get fingerprinted.
Licensing can also be attacked on the grounds that it is intended to fatigue people into forfeiting their civil rights. Especially since the MDGA failed to do anything about the current 7 "day" waiting period being a 7 week waiting period. Does anyone really think this license scheme will work any better?
The AWB gets attacked as a ban on firearms "in common use". We're in an especially good position these days, with police agencies being issued patrol carbines in lieu of shotguns. They cannot be considered military weapons. Any firearm that is legitimate for police use is legitimate for use by the general public.
we also have brian frosh on audio stating the licensing is expressely for the purpose if creating an undue burden. he says it over and over.
the exemptions for special people create a conflict with equal protection.
I'm actually hopefull that a lawsuit in sb281 will actually also effect md's previous law, and strike down regulated long guns and ballistic fingerprinting and the handgun roster board. omalley opened a can of worms.
md's old laws, made pre heller, needed a clean defendant to challenge. this new law post heller opens the door to challenge EVERYTHING.
there is a chance md comes out of this looking like pa or virginia.