Police in Washington, D.C. used a chemical irritant to disperse a crowd of people gathered Monday in Lafayette Square who vandalized monuments and buildings — after the City Council earlier this month passed a law, which has not yet taken effect, banning such substances for breaking up crowds at a "First Amendment assembly."

Social media posts from journalists in the area Monday night indicated that protesters attempted to set up a "Black House Autonomous Zone," or "BHAZ," similar to the "police-free" area set up in Seattle in recent weeks. Demonstrators also draped ropes over a statue of Andrew Jackson in an apparent attempt to pull it down and spray-painted "killer scum" on its pedestal, according to Reuters.

Police moved into the area and were quickly able to remove protesters, according to Fox 5 DC. But in doing so, both U.S. Park Police and D.C. police used a chemical irritant, which is a relatively common police tactic for dispersing unruly crowds, but one the Washington, D.C. City Council recently moved to ban in the wake of George Floyd's death and the unrest that followed.

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The legislation, passed unanimously earlier this month but not yet in effect as it's been sent to Mayor Muriel Bowser for review, says that "[c]hemical irritants shall not be used by MPD to disperse a First Amendment assembly." It also limits D.C. law enforcement's ability to use riot gear and bans "less-lethal projectiles," which are also commonly used when dealing with crowds like the one in Lafayette Square Monday night. And it requires the D.C. mayor to request that federal law enforcement in the district follow the same procedures as the city's police department.

Police were wearing riot gear but there were no reports of projectiles being used against protesters. It's unclear if the gatherings could have been cleared another way.

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At the time the law was passed, Bowser expressed suspicion of the council's expedited effort to pass major police and justice reform without time for public comment and debate.

"As we move to consider policing and potential reforms, I urge the council to allow a process where these issues can receive robust public discourse, which I believe will only help to increase community buy-in on any proposed reforms," she said.

"I am especially concerned that the Comprehensive Policing and Justice Reform Emergency Amendment Act of 2020 and the proposed amendments that I have been made aware of, amend laws related to issues like body-worn cameras, laws which received significant consideration and public input when they were crafted, and now would be significantly changed by emergency legislation."

Despite her concerns –­ and the fact she has not yet signed the bill –­ WJLA reported earlier this month that Bowser plans to sign the council's police reforms.

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The D.C. Police Union more pointedly warned that the bill was being rushed "to capitalize on the momentum of public sentiment, which will prevent a thoughtful and technical approach to various aspects of its impact on community policing." It also said that the bill "created a dangerous path to unchecked violence in the District."

Fox News has confirmed that during Monday's unrest the U.S. Secret Service asked reporters to leave the White House grounds nearby. The specific reason wasn't clear.

Additionally, the historic St. John's Episcopal Church, often called the Church of the Presidents, was vandalized with "BHAZ" spray-painted on its pillars. The church became the center of controversy earlier this month when President Trump posed for a photograph in front of the fire-damaged building after police cleared out protesters.

Chemical irritants were used in clearing out the area before Trump's photo-op, which outraged many and was a contributing factor in the District's ban on the substances.

Fox News' Edmund DeMarche and Louis Casiano contributed to this report.