wherever you live? actually...you could claim that your son delivering alcohol to that guy is against the law cuz he's not a "parent", "bos" or "caregiver". just say you're trying to protect your son and you want to obey the law where you live.

here's summary of CA law regarding your situation:

2.2. You possessed the alcohol for an approved limited purpose

Business and Professions Code 25662 -- California's minor in possession law -- provides an exception for authorized possession for a limited purpose.

If you are under 21 and are delivering alcohol under the direction of

your parent or other caregiver, or
pursuant to your job,
this will serve as a complete defense to a California MIP charge. 13

Example: You are a delivery boy for a local convenience store. Your boss instructs you to take a variety of items, including a six-pack of beer to a customer. Because you are obeying his orders...and are doing so pursuant to your job...you are not guilty of violating this law.
But note, the fact that you possessed alcohol for this limited purpose is what's known as an affirmative defense which means that it is up to you (through your attorney) to prove that you fell within this authorized exception.