Md. Code, Public Safety § 14–1002

(a) A county or municipal corporation is not liable under § 14-1001 of this subtitle for theft, damage, or destruction that occurs in a riot unless the authorities of the county or municipal corporation:

(1) had good reason to believe that the riot was about to take place or, having taken place, had notice of the riot in time to prevent the theft, damage, or destruction; and

(2) had the ability, either by use of the county’s or municipal corporation’s police or with the aid of the residents of the county or municipal corporation, to prevent the theft, damage, or destruction.

(b) A person may not recover damages from a county or municipal corporation under § 14-1001 of this subtitle if it is satisfactorily proved that the authorities of the county or municipal corporation, and the residents of the county or municipal corporation when called on by the authorities, used reasonable diligence and all the powers entrusted to them to prevent or suppress the riot.