The U.S. Department of Justice is suing the city of Rochester over its sanctuary city policies.

Court paperwork shows the suit stems from an incident in March in which Rochester police officers assisted federal agents in detaining three people during a traffic stop. One of them was charged with illegal entry into the U.S.

Mayor Malik Evans and Rochester City Council President Miguel Melendez, both of whom are named in the lawsuit paperwork, said the officer's actions violated Rochester's sanctuary city policies.

The DOJ's lawsuit claims those policies violate the supremacy clause of the Constitution, and seeks an injunction to stop them.

“To most Americans, that would look like law enforcement at its finest,” the lawsuit said. “But not to those leading the city of Rochester.”

The mayor responded to the lawsuit on Friday.

"The city of Rochester's policies have been around since I was 6 years old — going back to 1986. Any lawsuit that we get, you better believe that we will vigorously defend them in court as we do with all lawsuits," said Evans. "But I will tell you that this seems like this is just another distraction that we're getting from the federal government, there's been a lot of them, as we know, across the country, as it relates to many topics."

Rochester established itself as a sanctuary city in 1986 and reaffirmed the designation during Donald Trump's first term with a unanimously passed City Council resolution. The 2017 resolution says the police “shall not engage in certain activities solely for the purpose of enforcing federal immigration laws, including not inquiring about the immigration status” of crime victims or witnesses unless needed for a criminal investigation. It also prohibits city employees from assisting in federal immigration enforcement.

The Associated Press contributed to this report.