California Code, Business and Professions Code - BPC § 25659

For the purpose of preventing the violation of Section 25658, any licensee, or his or her agent or employee, may refuse to sell or serve alcoholic beverages to any person who is unable to produce adequate written evidence that he or she is over the age of 21 years.  A licensee, or his or her agent or employee, may seize any identification presented by a person that shows the person to be under the age of 21 years or that is false, so long as a receipt is given to the person from whom the identification is seized and the seized identification is given within 24 hours of seizure to the local law enforcement agency that has jurisdiction over the licensed premises.  A licensee, his or her agent or employees decision to not seize a license shall not create any civil or criminal liability.