PORTLAND, Ore. — Attorneys for Oregon argued Wednesday for a restraining order against federal agents deployed to quell protests in Portland — a standoff that some legal experts have warned could lead to a constitutional crisis in an election year.

A federal judge heard arguments from the state and the U.S. government in a lawsuit filed by Oregon Attorney General Ellen Rosenblum, who accuses federal agents of arresting protesters without probable cause, whisking them away in unmarked cars and using excessive force. Federal authorities have disputed those allegations.

The lawsuit is part of the growing pushback to President Donald Trump sending federal agents to Portland and announcing they'd also be going to Chicago and Albuquerque, New Mexico, to fight rising crime, a move that's deepening the country's already considerable political divide. Democratic mayors of 15 cities condemned the use of the agents in a letter to the U.S. attorney general.

The court hearing focused on the actions of more than 100 federal agents responding to protests outside Portland's Mark O. Hatfield Federal Courthouse, which has been a target for more than 50 nights of demonstrations against racial injustice following the killing of George Floyd at the hands of Minneapolis police.

The motion for a temporary restraining order asks U.S. District Judge Michael Mosman to command agents from the Department of Homeland Security, the Customs and Border Protection, the Federal Protective Service and the U.S. Marshals Service to immediately stop detaining protesters without probable cause, to identify themselves and their agency before arresting anyone, and to explain why an arrest is taking place.

During the hearing — held by videoconference because of the coronavirus pandemic — the state acknowledged that federal agents have the right to defend the courthouse but argued that they had overstepped.

Rosenblum, the state attorney general, said she was asking the court to "declare it not acceptable for federal officers to use unconstitutional, police state-type acts to detain citizens of Oregon without cause."

David Morrell, an attorney for the U.S. government, called the motion "extraordinary" and told the court it was based solely on "a few threadbare declarations" from witnesses and a Twitter video.

"The Hatfield courthouse did not damage itself," he said, calling the protests "dangerous and volatile."

It's not clear when Mosman will rule, but he challenged the state on whether it had the standing to ask for the restraining order. The judge noted that past legal decisions have required a state to establish a very high bar — "quasi-sovereign interest" — to successfully sue the U.S. government.

Attorneys for Oregon contended they had met that bar because the actions of the federal agents could erode residents' trust in all law enforcement, including state and city officers.

Morrell, the U.S. government attorney, disputed that, saying successful lawsuits usually involved issues that affected many people, not "highly individual interests" like the arrests.

The lawsuit is one of several filed over authorities' response to the Portland protests. On Thursday, a judge will hear arguments in a legal challenge that the American Civil Liberties Union filed on behalf of journalists and legal observers who say they were targeted and attacked by Portland police while documenting demonstrations. A freelance photographer covering the protests for The Associated Press submitted an affidavit that he was beaten with batons, chemical irritants and hit with rubber bullets.

U.S. Judge Michael Simon previously ruled that journalists and legal observers are exempt from police orders requiring protesters to disperse once an unlawful assembly has been declared. Federal lawyers say that journalists should have to leave when ordered.

The Portland City Council on Wednesday banned city police from cooperating with federal agents or knowingly arresting reporters or legal observers.

Meanwhile, a fence went up around the federal courthouse, where protesters and federal agents had clashed again overnight. Protesters repeatedly tried to break into the building and set fires around it, and the federal agents drove them back with tear gas and stun grenades, police said.

Far from tamping down the unrest in Portland, the presence of federal agents has energized the nightly protests.

Mayor Ted Wheeler's office said he would attend the protests Wednesday night and there would be "some form of dialogue" with the demonstrators. The Democrat has vocally opposed the federal presence in Portland but has still faced harsh criticism from many sides. Some, including fellow council members, have accused him of not reining in local police, who used tear gas before federal agents arrived. Others, including business leaders, have condemned him for not bringing the situation under control.

One group that has been prominent in the protests, the Pacific Northwest Youth Liberation Front, told the mayor to stay away.

The use of federal agents against the wishes of local officials — and the threat that it might be done elsewhere — was deepening the country's already considerable political divides and potentially setting up a constitutional crisis months ahead of the presidential election. The standoff could escalate after Trump announced Wednesday that he would be sending federal agents to combat crime in Chicago and Albuquerque, New Mexico, which are both led by Democrats.

The mayors of Chicago, Portland and other Democratic-led cities objected to such deployments and called them politically motivated in a letter to Attorney General William Barr and Department of Homeland Security Acting Secretary Chad Wolf.

Federal authorities have defended their response, saying officials in Oregon had been unwilling to work with them to stop the vandalism against the the U.S. courthouse and violence against federal officers.

Wolf said Tuesday that agents have been assaulted with lasers, bats, fireworks, bottles and other weapons. While he said federal agencies have made 43 arrests since July 4, he disputed they were done by unidentified agents, noting they have the word "police" on their uniforms.

Among the protesters was Maureen Healy, who joined a march Monday as people sang songs and chanted the names of Black lives lost.

Just after midnight, she saw a line of authorities wearing camouflage and dark outfits advance on the crowd. Protesters retreated, and Healy said she heard bangs, saw smoke and was struck by a projectile. She went to the hospital with a black eye, a cut to her face and a possible concussion.

"I was protesting peacefully, so why did federal troops shoot me in the head?" asked Healy, 52, who is chairwoman of the history department at Lewis & Clark College.

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This story has been updated to correct the federal agency's name to Customs and Border Protection.