The tense standoff between demonstrators and U.S. federal police dispatched to Portland, Oregon, dragged on Thursday after the city's mayor was tear-gassed by U.S. government agents as he made an appearance outside a federal courthouse during protests.

Mayor Ted Wheeler and hundreds of others Wednesday night were objecting to the presence of federal police sent by President Donald Trump, who labeled the demonstrators as "agitators & anarchists" after Wheeler was gassed.

Late Thursday a federal judge specifically blocked federal agents from arresting or using physical force against journalists and legal observers at the ongoing Portland protests. The lawsuit was filed by the American Civil Liberties Union.

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 had said that journalists should have to leave when ordered.

"This order is a victory for the rule of law," Jann Carson, ACLU of Oregon's interim executive director, said in a statement.

On Wednesday night Portland Mayor Ted Wheeler, a Democrat, appeared slightly dazed and coughed and said it was the first time he'd been tear-gassed.

It wasn't immediately clear if the agents knew Wheeler, a 57-year-old sixth-generation Oregonian and longtime politician, was among those in crowd when they used the tear gas.

Earlier in the night, Wheeler was mostly jeered by protesters as he tried to rally the demonstrators who have clashed nightly with federal agents. But they briefly applauded when he shouted "Black Lives Matter" and pumped his fist in the air.

Wheeler has opposed federal agents' presence in Oregon's largest city but has also faced harsh criticism from the protesters, who yelled and swore at him.

Ignoring the pushback, Wheeler told those who gathered outside the courthouse that he wanted to "thank the thousands of you who have come out to oppose the Trump administration's occupation of this city."

U.S. Department of Homeland Security acting Secretary Chad Wolf denied that federal agents were inflaming the situation in Portland. He told media that Wheeler legitimized criminality in the city by going to the front of the crowd of demonstrators where the fires were lit and that people were trying to pull down a fence erected to shield the federal courthouse.

Wheeler did not participate in lighting any of the fires or attempting to tear down the fence and was surrounded by his security team when he was gassed.

Earlier, protesters held signs saying "Tear Gas Ted" in a reference to Wheeler and his leadership of the Portland Police Bureau, which used the substance on protesters before federal agents arrived in the city in early July. As Wheeler left the protest zone about 12:40 a.m. Thursday, one person shouted that he should be there "every single night."

Wheeler's appearance in the protest zone came hours after state attorneys for Oregon urged a judge to issue a restraining order against agents deployed to tamp down on the protests.

Cover image via Reuters