U.S. District Judge Susan Bolton held Maricopa County Sheriff Joe Arpaio in criminal contempt of court Monday.
Arpaio did not follow orders from a judge to stop traffic patrols that targeted immigrants and reportedly continued to do so for 18 months after the judge's orders. Arpaio was found in civil contempt of court by a different judge in May.
The ruling followed a trial in which the Department of Justice argued that Arpaio had intentionally violated a federal judge's orders halting Arpaio's immigration roundups. Arpaio's lawyers had argued that the order was not clear and that he did not mean to violate the order.
The conviction is a misdemeanor, and the sentencing phase will begin Oct. 5.