Maryland Code, Alcoholic Beverages and Cannabis § 2-504

(1) supply service personnel, including bartenders and waiters;

(2) ensure that the service personnel are present at all times during the catered event;

(3) have at least one individual at the catered event who has been certified by an alcohol awareness program under § 4-505 of this article;

(4) ensure that the sale of food represents at least 70% of the total cost of the catered event; and

(5) return all unopened containers of alcoholic beverages to the holder's principal place of business at the end of the catered event.

(b)(1) The holder of a general statewide or limited statewide caterer's license may not:

(2) To ensure product integrity, a partially used keg of a malt beverage may not be used at another catered event.