Denver Mayor Mike Johnston signed an executive order Thursday that’s intended to protect protesters demonstrating against U.S. Immigration and Customs Enforcement operations if the city becomes the next target for a surge of agents.

His order requires Denver Police Department officers to intervene and detain ICE agents if they see any using “excessive force.” It also bans the federal agents from using city-owned property for their operations.

Standing in front of the City and County Building in downtown Denver, Johnston told reporters that his goal with the order wasn’t to provoke President Donald Trump. He said he didn’t have any information about whether ICE or the Trump administration intended to send an influx of agents to the city anytime soon.

“My first job is to run this city,” he said. “But in today’s America, that means answering questions from our residents about what happens if ICE troops descend on our city.”