I think the tough part of enforcing this would be the advanced amateurs that are also dog owners. I know plenty that take photos ringside and sell very cheap or give them away to other owners. Now, are they breaking rules under this first thought or not?

They would have to print in the program that no cameras would be allowed without the vendor fee and that surely would NOT make owners happy. I know as an owner/mother that venues my kids/dogs are competing, I expect the right to take photos

Its altogether tough. I see many sides of the issue. I could argue for, against, back and forth. It just could not FAIRLY be enforced