http://www.dnr.state.md.us/wildlife/captive.html
MORE ABOUT COMMERCIAL TRADE
Commercial trade in native reptiles and amphibians requires a permit. A permittee may sell, offer for sale, trade, or barter any reptiles or amphibians from Lists A and B (only turtles with a carapace length of at least 4 inches) if the animals are captively produced or legally obtained from out of state. In accordance with Maryland Health Department regulations, viable turtle eggs and turtles with a carapace length of less than 4 inches cannot be imported, transported, sold, bartered, bred or possessed.
Here's the COMAR: https://constmail.gov.state.md.us/comar/10/10.06.01.23.htm
"D. Penalties and Seizure of Contraband Reptiles.
(1) Pursuant to Health-General Article, §§18-219 and 18-222, Annotated Code of Maryland, a person who imports, transports, sells, transfers, breeds, raises, keeps, or possesses any live turtle with a carapace length of less than 4 inches, other reptiles, or reptile eggs in violation of §§A—C of this regulation is guilty of a misdemeanor and on conviction is subject to a fine not exceeding $500, or imprisonment not exceeding 1 year, or both.
(2) An authorized law enforcement officer may seize a turtle with a carapace length of less than 4 inches, viable turtle and other reptile eggs, and other reptiles, which are considered a nuisance and a contraband pursuant to Health-General Article, §18-222, Annotated Code of Maryland, and §A of this regulation."