If an intoxicated customer refuses a cab or refuses to allow a friend to pick him up, what we must you do is you should inform local law enforcement.
Step-by-step explanation:
If a customer is intoxicated, intimate to the management and offer he/she to call his /her friend or arrange a cab for home.
Consider their safety as the prior most thing and wait till the law enforcement arrives even the customer refuses offers of a cab or refuses to allow a friend to pick them up. Also Try to delay the process to customer so they should not leave before law enforcement arrives.