Former California Gov. Arnold Schwarzenegger on Monday called the federal judge overseeing the Trump University lawsuits an "American hero."

The Austrian-American actor, who's a Republican, spoke out about U.S. District Judge Gonzalo Curiel on Twitter, whom he appointed to the California superior court.

Judge Curiel is an American hero who stood up to the Mexican cartels. I was proud to appoint him when I was Gov. https://t.co/ADLCBXw57Q — Arnold (@Schwarzenegger) June 6, 2016

President Obama later appointed him to the U.S. district court in the Southern District of California. Donald Trump has come under fire for suggesting Curiel is biased in the Trump University case because he is of Mexican descent and belonged to a Latino lawyers association. Trump told The Wall Street Journal that these factors are "an absolute conflict" because he has vowed to build a wall along the U.S.-Mexico border.

Get Breaking News Delivered to Your Inbox

Ironically, Schwarzenegger will host the Celebrity Apprentice later this year. He told the Los Angeles Times that he has voted for John Kasich through a mail-in ballot in Tuesday's California primary even though Trump is the presumptive GOP nominee.