While the vast majority of protestors are peaceful, Koster said in a tweeted statement, "law enforcement has repeatedly encountered groups employing violence against officers, businesses and threatening the citizens of Ferguson.

"Peaceful protest will continue, but the violence must stop," Koster said "This restriction (that protestors remain in a designated site) is as narrowly tailored as the gunfire and violence along West Florissant Avenue will allow."

The St. Louis County Police Department has publicly announced a designated protest area established at Ferguson and West Florissant avenues.

The ACLU says "there is widespread interest" the tactics, which the ACLU says "raise questions about whether a military response to protest is consistent with the values of the United States as well as the lack of transparency in the handling of the shooting investigation and response to the unrest."

The suit was filed on behalf of Mustafa Abdullah, a Missouri resident who was ordered five times in one hour to refrain from gathering or standing for more than five seconds, the ACLU said.