Milwaukee County Sheriff David Clarke further aligned with President Donald Trump’s immigration policies on Thursday, calling for the elimination of sanctuary cities by jailing mayors and governors who don’t comply.

“I’m telling you right now folks, you charge one mayor, one governor, one council president that adopts these laws, this stuff is going to end right away,” Clarke said during a speech at the Conservative Political Action Conference.

Clarke read U.S. code 1324, which puts criminal sanctions on anyone attempting to conceal persons living in the country illegally, “which is what sanctuary cities do,” he said.

The term refers to those cities that fail to cooperate with federal immigration enforcement officers seeking to make arrests of individuals in the country illegally.

The issue was thrust into the spotlight after the July 2015 shooting death of Kathryn Steinle, who was allegedly murdered by a man living illegally in the U.S. He reportedly had several felonies and was deported five times previously.

“President Donald Trump has made it very clear that it is high time — it is past time in America that we start aggressively enforcing the rule of law in America,” Clarke said.

Clarke argued that sanctuary cities are havens for criminal activity and they provide cover for “criminal illegal aliens to continue to prey on not only law-abiding people, but also illegal immigrants in this country.”

Illegal immigrants won’t report crimes committed against them for fear of deportation, Clarke said, which has lead to an underreporting of crime because of Sanctuary cities.

“That’s where the president is going to start: The deportation of criminal illegal aliens,” Clarke said. “I’ve made it clear that in helping President Trump get his arms around this serious problem of illegal immigration that I was going to use the resources that I have as the sheriff in Milwaukee County to help him accomplish that.”