I would assume it depended on how the law is worded and the definitions of a "handgun." According to the ATF, receivers and frames qualify as "firearms" and are subject to all the transporting and sales restrictions of a fully-functional firearm.
You'll have to see how MD defines a "firearm" or "handgun." If MD qualifies these frames and receivers as "firearms" or "handguns" then they would obviously fall under the same restrictions.
Sorry for what might seem like a non-answer.