When BYU established tailgating rules a few years ago I did some research to see how they compared with other schools across the country, particularly those with a strong tailgating tradition. I found that there was very little difference in the rules between schools.

It doesn't seem to be the rules that restrict the tailgating, but LDS culture and tradition. My guess is that you will find any rule about tailgating length to be one that was already there and one that is shared with many schools. I would also guess that it isn't enforced at BYU or other schools, but there on the books in case they need to address an individual problem and want something in the books that they can fall back on.