Most statutes tend to tell you what you can't do, especially in MD. Reading the statute that says you can't buy or sell and noticing that it doesn't mention "import" or similar is about the best you can do.
So, if for example, it says:
A person may not manufacture, sell, offer for sale, purchase, receive, or transfer a detachable magazine that has a capacity of more than 10 rounds of ammunition for a firearm.
That would leave the option of bringing in a mag you already own, or scooting over to VA, buying one, and bringing it home. You'd want to be pretty sure that there wasn't some other law banning importation, but the chances are pretty low that you would find a specific law stating "efeng9622 is allowed to bring his or her mags from Virginia"
One could also note that the so-callled "assault weapon" ban enacted at the same time as the above includes similar wording, but also includes an additional statement that one may not "transport an assault weapon into the state"