Clarification.... a person who lawfully possessed a listed "assault pistol" before June 1, 1994 may continue to transport and possess the weapon if it was registered with the Maryland State Police before August 1, 1994. Will look for the list of named assault pistols and post if I find it.
I'm going back over my recollection of this, and it is confusing. The Tec-9 is banned by name as is any other center-fire version. What I believe happened is they listed the Skorpion semiautomatic pistol and this got interpreted as covering the Tec-22 "scorpion". This is similar to what happened with the "Bushmaster" and everything else that shared the name name got banned by sloppiness. I distinctly remember getting a letter from the state police informing me that my Tec-22 was on the list and I could not transfer it in MD.
So there you go... clear as mud... just like every other gun law in the Old Line State.
MD-Legal or not, the other factor you should be aware of is they pretty much suck, LOLz.
They use 10/22 mags, but that's about the best part about them. They seem to be very prone to FTF, FTE problems, and are ammo sensitive on top of that. I had one made in the early 90's, back before the fed AWB, and it was junk. I can't imagine they got any better during the ban era.