City News Service reports Jason Michael Rouswell was charged with one count of deprivation of rights under color of law in connection with the 2016 assault outside a Social Security Administration office. The 46-year-old entered his plea in federal court on Monday.
He faces up to 10 years in federal prison at sentencing July 16.
Rouswell was an inspector with the Federal Protective Service that guards U.S. facilities.
Video of the incident showed a uniformed officer kicking a man lying face down on a street with his hands cuffed behind his back.