Under California law, all residents must be at least 21 in order to consume alcoholic beverages. Even if a minor doesn't consume alcohol, that doesn't mean he can legally enter an establishment that serves it. All bars are obligated to post clear and visible signs indicating the age requirement to enter.
Section 25665 of the California Alcoholic Beverage Control states that minors are not allowed to enter or remain within a bar. However, a minor is allowed to enter and remain inside a restaurant that happens to have a bar attached to it.
The Decoy Law
Under Section 25658 of the California Code of Regulations, law enforcers may use minors as decoys in order to catch bartenders and bars that are selling to those under the age of 21. Under the guidelines of the decoy program, all decoys must look under the age of 21, but be honest if bartenders question their ages. The California Supreme Court ruled in 1994 that the use of a decoy program was legal and did not classify as any form of entrapment.
California law states that any minor who is caught purchasing alcohol at a bar will be guilty of a misdemeanor. The minor will have to pay a fine of $250 and will be required to perform a minimum of 24 hours of community service.