Maryland Code, Public Safety § 13-214

(a) Except for the units of the organized militia and the troops of the United States, a body of persons may not associate as a military company or organization or parade in public as a military company or organization without the permission of the Governor.

(b) Except for troops acting under the authority of the President, an armed military force from another state may not enter this State for military duty without the permission of the Governor.