Eight of the employees were forced out of the agency, three were cleared of serious misconduct and at least two have been fighting to get their jobs back.
The incident took place before Obama arrived in Colombia and the service said the president's safety was never compromised. But news of the scandal broke during his trip, overshadowing the summit and embarrassing the U.S. delegation.
Sullivan issued a new code of conduct that bans employees from drinking within 10 hours of starting a shift or bringing foreign nationals back to their hotel rooms.
Sullivan apologized for the incident last year during testimony before a Senate panel.