Brandon Kiel, an aide of 50-year-old Harris, who worked as deputy director of community affairs at the California Department of Justice was arrested for impersonating a police officer.
Kiel, 31, who is reportedly on leave from his job, reportedly called himself the "chief deputy director" of the masonic Fraternal Police Department in letters to various southern California police departments requesting meetings.
The rogue police force claims to have existed for more than 3,000 years and have jurisdiction in 33 states and Mexico.
Harris, a rising star of the Democratic Party, is running for the Senate seat from California.