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Portland, Oregon, Mayor Ted Wheeler on Saturday ordered the city’s police to stop using a common type of tear gas except as a last resort in life-threatening situations, making it one of several cities that have started restricting law enforcement tactics in response to widespread protests over the killing of George Floyd.

Wheeler issued a statement saying he shares community concerns about the use of CS gas, especially during a respiratory-illness pandemic. Critics have called on the Portland Police Bureau to permanently ban the use of CS gas on protesters.

“I strongly believe that gas should not be used to disperse crowds of non-violent protestors or for general crowd management purposes,” Wheeler tweeted. “It should only be used in response to violence that threatens life safety.”

Seattle took a similar step Friday, with Mayor Jenny Durkan announcing a 30-day moratorium on the use of CS gas for crowd control — though pepper spray and other less-than-lethal measures remain available to officers.

Officials in Pittsburgh, New Orleans and Washington, D.C., have proposed bans or limits on the use of tear gas, and Minneapolis, where Floyd was killed, has halted the use of choke holds and neck restraints like the one that killed him. California Gov. Gavin Newsom ordered police there to stop training officers in choke holds, and Bellevue, Washington, Police Chief Steve Mylett on Friday banned his officers from using controversial neck restraints except when deadly force is needed.

In Denver, U.S. District Judge R. Brooke Jackson on Friday imposed restrictions on the use of chemical and less-lethal weapons by police, saying officers there had failed to police themselves when it came to using them. His order, as he modified it on Saturday, requires the use of such weapons to be approved by a supervisor with the rank of lieutenant or higher — and only in response to violence or property destruction personally witnessed by the supervisor.

The judge also ordered police not to aim the non-lethal weapons at people’s heads and groins. Videos of police firing pepper spray at protesters who were yelling but not acting violently “showed that the officers had ample time for reflection and were not dealing with dangerous conditions,” he said.

Denver police said the order was largely consistent with its use-of-force policy and that it would comply.

Police in Seattle were similarly criticized for overreacting to protests last week. Video from last Monday night showed police attacking mostly peaceful protesters with pepper spray after an officer tried to grab a pink umbrella from a demonstrator on the other side of a metal barricade.

The city has promised a thorough review of the department’s actions. More than 12,000 complaints poured into Seattle’s police accountability office.

Portland’s announcement came a day after the mayor said police would no longer use a “long-range acoustic device,” or LRAD, to disperse protesters. The device can emit high-pitched, loud frequencies and can cause hearing damage.

Police used it early Friday to disperse a small group of protesters who set fires, threw projectiles and pointed lasers at officers’ eyes after most peaceful protesters had gone home.

Portland police arrested about 20 people late Friday and early Saturday, alleging offenses that included disorderly conduct and interfering with an officer.