A U.S. District Court Judge ordered Denver police on Friday to stop using tear gas, plastic bullets and other "less-than-lethal" force such as flash grenades against protesters.
The temporary injunction was in response to a local lawsuit filed on Thursday in the Denver District Court by protesters complaining about excessive force used by officers during public demonstrations following the death of an unarmed black man, George Floyd, in police custody in Minneapolis last month.
The ruling cited examples of protesters and journalists being injured by police.
"Peaceful demonstrators' legitimate and credible fear of police retaliation is silencing their political speech," it said.
The death of Houston native Floyd during his arrest for a non-violent offense has touched off national protests against the use of force by police.
Video of Floyd's arrest show an officer holding his knee on Floyd's neck for almost nine minutes.
In Denver, throngs of marchers have gathered around the state Capitol every day for more than a week, chanting and carrying signs protesting Floyd's killing.
Some people among the mostly peaceful crowd broke windows in the state Supreme Court building and a nearby museum overnight on May 29. Some store front windows were smashed and looters made off with merchandise.
While the lawsuit, brought by four activists, acknowledged that some demonstrators "engaged in destructive behavior," and it also said the vast majority were peaceful.
"Nonetheless, the Denver Police Department ... and other police departments at their invitation, have engaged in injurious riot control tactics without issuing clear warnings and orders to disperse," the complaint said.
At least one woman sustained a serious eye injury when she was struck by a projectile, the lawsuit said.
The court ruling cited numerous instances, captured on video, of police using tear gas, projectiles and other measures against peaceful protesters engaged in their U.S. Constitutional rights to gather and protest.
Journalists were also specifically targeted and shot with projectiles, "while in the process of documenting the scene," the ruling said.
In his decision, U.S. District Judge R. Brooke Jackson said that Denver police had "failed in its duty to police its own."
"If a store's windows must be broken to prevent a protester's facial bones from being broken or eye being permanently damaged, that is more than a fair trade," Jackson wrote in his 10-page ruling.
"These are peaceful demonstrators, journalists, and medics who have been targeted with extreme tactics meant to suppress riots, not to suppress demonstrations."
Milo Schwab, an attorney for four of the plaintiffs, told Reuters that the ruling was "a humbling victory."
"This will ensure that people protesting police brutality are not subject to police brutality," he said. "Demonstrators in Denver are now safer from police brutality than anywhere else in the country."