((a)) Such stores as the Secretary of the Navy designates may be procured and sold to members of the naval service, members of the Coast Guard, and widows and widowers of such members.
((b)) The Secretary may, by regulation, provide for the procurement and sale of stores designated by him to such civilian officers and employees of the United States, and such other persons, as he considers proper—
((1)) at military installations outside the United States; and
((2)) at military installations inside the United States where he determines that it is impracticable for those civilian officers, employees, and persons to obtain those stores from private agencies without impairing the efficient operation of naval activities.