By Chris Kenning
(Reuters) - A federal judge ruled Wednesday that St. Louis police cannot shut down non-violent demonstrations and employ chemical agents to punish protesters, dealing a victory to a civil liberties group that challenged the police response to protests.
U.S. District Judge Catherine Perry issued her order following complaints of misconduct during protests that gripped the city after the Sept. 15 acquittal of white former officer Jason Stockley on murder charges in the killing of black suspect Anthony Lamar Smith, 24, in December 2011.
The American Civil Liberties Union of Missouri filed a lawsuit in U.S. district court in St. Louis on Sept. 22, alleging that police used excessive force and retaliated against people engaging in activities protected by the First Amendment.
Protesters cited anger over tactics including the use of pepper spray and "kettling," in which officers form a square surrounding protesters to make arrests. Some caught inside police lines said officers used excessive force.
The clashes evoked memories of riots following the 2014 shooting of a black teenager by a white officer in nearby Ferguson, Missouri.
On Wednesday, Perry issued a preliminary injunction limiting police tactics in responding to protests.
"Plaintiffs' evidence — both video and testimony – shows that officers have exercised their discretion in an arbitrary and retaliatory fashion to punish protesters for voicing criticism of police or recording police conduct," Perry wrote.
Koran Addo, a spokesman for St. Louis Mayor Lyda Krewson, said the city would comply with the order.
Tony Rothert, legal director of the ACLU of Missouri, said in a statement that the ruling was a win for the First Amendment.
The protests that followed the former officer's acquittal turned violent at times, with some demonstrators smashing windows and clashing with police.
But Perry, in her order, said police cannot declare an assembly unlawful and enforce it against those engaged demonstrations unless the persons pose an imminent threat of violence.
She also barred the use of pepper spray without probable cause to make an arrest and without providing clear warnings to protesters with a chance to heed them.
The judge also ordered both sides to mediation.
(Reporting by Chris Kenning; editing by Grant McCool)