Denver has joined 26 other local governments in an amicus brief supporting California Gov. Gavin Newsom’s legal challenge to President Donald Trump’s deployment of the National Guard and Marines in Los Angeles. 

“In Denver, our residents are connected with police who live on the same streets they patrol and with officers who grew up in the same communities they’re sworn to protect. That’s why our crime rates are plummeting,” Mayor Mike Johnston said in a statement. “What the Trump Administration is doing in Los Angeles and Washington, D.C. isn’t a strategy for fighting crime. It’s a federal police state meant to sow chaos, cause disruption, and strip rights away from local governments and citizens.”

An amicus brief is a legal document that allows a party to provide an outside perspective on an issue under litigation. 

In the brief filed on Tuesday, Denver argues that the deployment of military troops for policing purposes “dramatically increases the risk of irreparable injury to constitutional sovereignty promised by the 10th Amendment, the fundamental constitutional rights of residents, and the general welfare of the public.”

The city also asserts to the court that local police departments are better suited to serve residents while protecting their rights under local, state and federal laws.

During an Aug. 27 Reddit “Ask Me Anything” session, Johnston called Trump’s “militarization” of the nation’s cities “unprecedented” and “dangerous.” He promised to take the administration to court “on Day One” should the White House send federal troops to Denver. 

“Any first-year law student in America could tell you that deploying the U.S. military on the streets of American cities in times of peace to enforce domestic law is clearly illegal,” the mayor posted. “Denver does not need any help from the National Guard, as we are seeing the largest decrease in violent crime of any top 50 city in the country.”

After the Trump administration deployed thousands of National Guard soldiers and Marines to Los Angeles following protests over immigration raids, Newsom, a Democrat, sued, arguing the president’s actions violated federal law.

On Sept. 2, U.S. District Court Judge Charles Breyer ruled in a 52-page opinion that Trump’s decision to deploy troops in Los Angeles was illegal.

The federal court’s ruling against the Trump administration’s use of the National Guard troops in California does not automatically apply to other states.

Republican strategists contend Democrats are in a bind over how to react to Trump’s directive based on high crime rates in Democrat-led cities. FBI data show that 19 of the 20 cities with the highest murder rates and at least 100,000 residents in 2024 had Democratic mayors.

The National Police Association earlier said it welcomes more “boots on the ground,” referring to Trump’s executive order creating a series of specialized military units within the National Guard that, under the direction of Secretary of Defense Pete Hegseth, would be “specifically trained and equipped to deal with public disorder issues.”

The Trump executive order is a positive step toward rectifying a decrease in “boots-on-the-ground law enforcement” over the past decade, National Police Association spokesperson Betsy Brantner Smith told technology publication Smart Cities Dive.

“The order declares that safe communities depend on a tough and well-equipped police force,” she told the publication. “That’s something that the president has said with some frequency — let cops be cops.”

Denver recently filed a motion to dismiss the Trump administration’s lawsuit against the city and state, claiming it was an unlawful attempt to overturn local policy on immigration. The city has also filed four lawsuits against the administration.

This summer, the city was granted a preliminary injunction preventing Trump’s threats to withhold hundreds of millions of dollars in allocated transportation funding.

The city also joined Chicago and Pima County, Arizona, in seeking to recover $24 million in FEMA dollars allocated for the purposes of sheltering and assisting migrants. 

That case is still pending.

The city has also received a favorable ruling in two other cases where the administration has threatened to withhold federal dollars – one over so-called “sanctuary jurisdictions” and the other over funding to prevent large-scale security threats.