Sucks, but you are totally being a great parent by enforcing the rules. He knew the consequences, and messed up anyway. So now he'll learn a lesson.
When I was in 8th grade (for some reason that was my "rebellious" year), I did a couple things like that. My dad did the same stuff, and I was so mad at him at the time. But I realized a few years later, I think he was an awesome dad, he was really being a good, loving parent as you're being.
