Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 33, § 130

The commander-in-chief may prescribe rules and regulations under which bodies of citizens of the United States, or foreign troops to whose admission to the United States the government of the United States has consented, may drill or parade with firearms or harmless imitations thereof. The commander-in-chief may authorize the use by any such body of any state armory or air installation for drill or training.