The embattled mayor placed Calkins and Massey on paid administrative leave on March 22 pending an investigation into what Sun called harassment and intimidation.
"I know I put them on administrative leave to avoid a tremendous liability for the city," Sun said at the time. He wouldn't give a specific reason for the move, claiming only that it was "an internal safety measure."
Both men appealed to the Civil Service Commission, which has power under state and local laws to consider appeals of suspensions against civil service employees.
The commission determined that Sun did not follow proper procedure in putting the men on leave, including failure to notify each man why they were suspended, and ruled their suspensions invalid. They ordered Sun to reinstate the two men immediately.
Thursday, Sun announced he was hiring former University of California-Davis police chief Annette Spicuzza to be in charge while Calkins was on leave. It is not clear what effect the commission's ruling will have on Spicuzza's hire.
Sun has been at odds with his police department and other staff members since he took office in 2011.