The State of Washington requires ID for proof of age to go onto any establishment that serves alcohol. I have been in establishments where the Stare Liquor Control Board representative has asked every single person in the establishment was asked for ID. In addition in this state at least business owners have the right to refuse service in certain cases, i.e., the patron is under the influence, the patron is causing trouble, the patron is annoying other guests.
Washington State law requires checking of identification only for "youthful appearing people."
Tell the Liquor Control Gestapo to go suck an egg.