A California Highway Patrol officer arrested Ruiz, a 25-year veteran of the force, on the 101 Freeway in Sherman Oaks shortly before 1:30 a.m. on May 30.
The LAPD won't discuss the arrest, but has confirmed that Ruiz is no longer running the Rampart station and has been reassigned pending an investigation.
Ruiz was reportedly not taken to jail. His vehicle was impounded and he was released to a friend or family member.
The Associated Press contributed to this report.