Police in Seattle have been ordered to stop using tear gas, pepper spray and stun grenades to break up protests.
The court ruling was a victory for groups who say authorities have overreacted to recent demonstrations over police brutality and racial injustice.
US District Judge Richard Jones sided with a Black Lives Matter group that sued the Seattle Police Department this week to halt the violent tactics officers have used to break up protests.
Police used tear gas, pepper spray and other force against crowds of protesters last weekend, and the judge’s order halts those tactics for two weeks, though demonstrations this week have been calm.
Mayor Jenny Durkan and Police Chief Carmen Best have apologised to peaceful protesters who were subjected to chemical weapons, but Ms Best said some demonstrators violently targeted police, throwing objects and ignoring orders to disperse.
The judge said those objecting to police tactics made a strong case that the indiscriminate use of force is unconstitutional.
He said weapons like tear gas and pepper spray fail to target “any single agitator or criminal” and are especially problematic during the coronavirus pandemic.
“Because they are indiscriminate, they may even spill into bystanders’ homes or offices as they have done before,” he wrote.
Ms Durkan, a former lawyer, “believes the court struck the right balance to protect the fundamental constitutional right to exercise protest, with the need to also ensure public safety”, spokeswoman Kamaria Hightower said.
This week, demonstrators have turned part of Seattle’s Capitol Hill neighbourhood into a protest centre with speakers, drum circles and Black Lives Matter painted on a street near a police station.
Police largely left the station after the chaos last weekend, when officers tear-gassed protesters and some demonstrators threw objects at them.
Ms Durkan tweeted about her visit to the so-called autonomous zone, which has been criticised by US president Donald Trump and where people, including officers, come and go freely.
Mr Trump took aim at her and Washington state governor Jay Inslee for not breaking up the occupation by “anarchists” and threatened to take action if they do not.
Michele Storms, executive director of the ACLU (American Civil Liberties Union) of Washington, said the group was pleased with the judge’s ruling.
“The city must allow for freedom of speech and freedom of assembly, and it must address police accountability and excessive use of force,” she said in a statement.