D.C. Code § 37-201.09
No person, firm, or corporation shall erect, operate, or maintain, or cause to be erected, operated, or maintained within the District of Columbia any coin-in-the-slot machine or automatic vending device without placing in charge thereof some responsible person. No such machine shall be maintained for use when the same is not in perfect working order, and the person in charge as well as the owner of such machine or device shall be held responsible for operating or maintaining any such machine or device which is not in perfect working order. A sign or placard shall be placed on every such machine or device in a conspicuous place and shall contain the name and business address of the owner and of the person in charge of such machine or device, and shall state that the person in charge of such machine or device will refund to any person money deposited by him for which the commodity or service promised expressly or impliedly has not been received, and such person shall so refund such money.
D.C. Code § 37-201.09