Judge for yourself. Here's how the pertinent MARYLAND law will read as of October 1, 2013:
CRIMINAL LAW
TITLE 4. WEAPON CRIMES
SUBTITLE 3. ASSAULT PISTOLS AND DETACHABLE MAGAZINES
Md. CRIMINAL LAW Code Ann. § 4-305
§ 4-305. Detachable magazines -- Prohibited
(a) Scope of section. -- This section does not apply to a .22 caliber rifle with a tubular magazine.
(b) Prohibited. -- 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.
Possesion is not ruled out. Basicly if you have them.. then they are Grandfathered in.. That's means don't get pulled over with them in a bag with a receipt proving you just bought them!