My sorority has strict policies regarding alcohol, and I believe all the other NPC sororities on campus do too. Since we have a dorm dedicated to sorority housing, our dorm is technically supposed to be alcohol-free. It so isn't though.
I agree with what someone said about some sororities not being as strict, so the others will break the rules just be competitive in recruitment.
It really bothers me that some chapters on my campus get caught and punished for relatively minor offenses, yet I see others violating the rules ALL THE TIME, and they never get caught.