Stumping for Hillary Clinton in Cleveland on Thursday, President Barack Obama reminded her Republican opponent that politicians cannot threaten to jail public figures in a democracy.

“We have fought against those kinds of things,” the president said, digging at Donald Trump’s grasp of the U.S. Constitution. “We say in a democracy you can’t threaten to jail your opponents. There are things called due process. In a democracy, you can’t just ban reporters or press that you don’t like because there’s this thing called the First Amendment. In a democracy, you have a contest but if you lose, then you say congratulations and you move on because the country and our system of government is bigger than any single individual.”

Trump has attacked the FBI for declining to prosecute Hillary Clinton for her use of a private email server as secretary of state, claiming that any other person would be in jail. “Lock her up!” has been a rallying cry at Trump rallies for months, and the Republican nominee promised to do just that at the second presidential debate on Sunday. Trump pledged to sic the Justice Department on Clinton and told her that if he won the election, she’d “be in jail.”

The real estate mogul has also banned reporters whose coverage he deemed unfair from campaign rallies and warned supporters that the election results will be “rigged” in Clinton’s favor unless they monitor polling stations.

Current and former government officials from both sides of the aisles have condemned his remarks as irresponsible and dangerous.

Obama criticized Republican leadership for allowing Trump to get away with comments like this for so long.

“I’m disturbed about Republican elected officials who know better but are still supporting this guy,” the president told the audience in Cleveland.