I apologize if this has already been answered correctly, as I didn't read this entire thread. You are absolutely allowed to bring preseasoned meat and/or cooked meat to a contest. Your contest meat is separate. The inspector will only ask to see your competition meat. The organizers, reps, meat inspectors know that folks have parties on Friday night.
While we're on the topic though, let's be honest, if somebody wants to cheat, they can. There are always going to be ways to cheat. If it means that much to people, so be it. After all, they are the ones that have to live with themselves. There are too many good, honest people at barbecue contests to think that cheating is wide spread. I have met so many great folks cooking. Cheating or not, you still have to cook the stuff.
Go out and have a good time. Be friendly to the folks that pass by and be courteous to your neighbors. That's really what it's all about, isn't it?