Speaking as a flight attendant for AA, I have had captains tell me during the preflight briefing that they don't want the forward lav used during boarding and they didn't want coach passengers to use the first class lavs at all during the flight, which is against our policy. The way I look at it, he's in charge and when one of these guys does this, I write it up on a report just in case it comes back to bite me in the butt.

Mike-BOS