WASHINGTON -- Police overseeing security at protests in Ferguson, Missouri, in August violated the constitutional rights of demonstrators and journalists by forcing them to stay in constant motion and not stop walking, a federal judge ruled on Monday.

Chief U.S. District Judge Catherine D. Perry held that the "practice of requiring peaceful demonstrators and others to walk, rather than stand still, violates the Constitution." She issued a preliminary injunction banning St. Louis County Police and Missouri State Highway Patrol officers from using the tactic.

"The evidence from plaintiffs witnesses shows that the police, including those from St. Louis County, told many people who were either peacefully assembling or simply standing on their own that they would be arrested if they did not keep moving," wrote Perry, who sits on the U.S. District Court for the Eastern District of Missouri. "Some law enforcement officers told people that they could stand still for no more than five seconds. Others gave instructions that people were walking too slowly, or that they could not walk back and forth in a small area. Some law enforcement officers did not make people keep moving, others did. Some officers applied the strategy to reporters, others did not. Many officers told people who were standing in small groups on the sidewalks during the daytime hours that they would be arrested if they did not keep moving."

Perry ruled that individuals who wished to gather "in the wake of Michael Browns tragic death have a constitutional right to do so." She also noted that "they do not have the right to endanger lives of police officers or other citizens." She said that nothing in her order restricted the ability of police officers to do their jobs.

Vague rules that are applied in a haphazard fashion tend to increase community tension, Tony Rothert, legal director of the American Civil Liberties Union of Missouri, said in a statement. Judge Perrys injunction is a huge win for peaceful protesters and those who believe in the rule of law." The ACLU chapter had brought suit over the issue.

The "keep walking" or "five-second" rule was implemented in Ferguson on Aug. 18. Police officers would not allow anyone to congregate, even on public sidewalks, even in broad daylight.

Highway Patrol Capt. Ron Johnson defended the practice at the time, saying the police were "not violating your rights . We're allowing you to protest." The federal judge disagreed.

During a hearing last month, St. Louis County Police Chief Jon Belmar said that the keep-walking rule was never meant to be enforced during the day and that there had been a miscommunication over the issue.