Not only is this an idiotic action by the State Police of the People's Republic of Maryland,

you'll note they haven't actually let dealers know about this stupidity:
Maryland --(AmmoLand.com)- In its infinite wisdom, the licensing division of the Maryland State Police has determined that certain .22 caliber rimfire rifles are “assault weapons” based solely upon there cosmetic resemblance to some firearms that are defined by Maryland law as “assault weapons.”
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The real problem is: The Maryland State Police have apparently not issued a formal written bulletin to the firearms dealers informing them of this new requirement. It is entirely possible for a dealer and/or buyer to be arrested, charged, and prosecuted for violating an unwritten policy established in secret by Maryland State Police Licensing Division.

I repeat: you could not pay me enough to live in that state; they keep electing dirtbags like Frank to the Congress, and they elect state politicians who encourage the State Police(very apt name for them) to do crap like this.

Couple of years back a friend told me of driving through the People's Republic of Maryland and being stopped by the State Police. And the main reason for the stop seemed to be "Where are the guns?"
"Excuse me?"
"You assholes from Texas and Oklahoma always have guns, now where are they!"
Very bad attitude, very threatening. No, I have no proof of it. After hearing so many stories like this, and of how subjects of the PROM are treated, I believe it.