Twenty-one businesses in Petaluma were cited for serving or selling alcohol to a minor in a sting operation conducted over three days.
The state Department of Alcoholic Beverage Control on Friday announced the results of last week's sting in which a total of 76 on-sale and off-sale locations were checked.
The "minor decoy operation" involves the use of an underage person under the supervision of department agents, attempting to buy alcohol from retail establishments.
The employees who sold to the minor were cited and released for selling or furnishing alcohol to a minor, a misdemeanor.
The establishments are subject to administrative action by the ABC, ranging from a fine to suspension or revocation of their license.
Decoy operations have been conducted by local law enforcement throughout California since the 1980s and were upheld by the state Supreme Court in 1994.