It has nothing to do with proximity to campus. All greek organizations on campus need to follow certain rules. Thats why some greeks choose not to be affiliated.
Actually it does. Because many of the fraternity houses are located on or near College Ave, RUPD has jurisdiction. Whenever an organization has a "social event," they are right across the street waiting for it to get out of control so they can shut it down. If they're found to have broken any rules (i.e. no kegs in houses, any injuries, hospitalizations), it can then lead to discipline by the school. RUPD patrols off campus, but only to tip off NBPD about satellite house parties. They usually shut down the party, hand out a noise violation ticket, and move on. And no organization is punished because of it.