House Rules.
That's it. That's my answer.
Your son is playing you Both. He is one of many kids with a Mom's House and a Dad's House, and he should know by now, it's House Rules.
It's ok if the rules are different in each house. The rule for your son to remember is to follow the rules of each house. It's actually been studied that kids in divorced/separated families learn adaptability better than their peers in One Household.
Your house, your rules. He should know, at 13, better than to push it. But he did, and he got away with it. This Time. As an ACOA, I'll tell ya: it's easy to blame the drunk.