Tribal police in South Dakota have arrested three Native Americans who set up a roadblock to keep alcohol out of an Indian reservation.
Duane Martin was wrestled to the ground
Oglala Sioux police told the activists that they had no authority to stop and search cars at Pine Ridge reservation.
The detained organisers - including one who allegedly carried a spear - were charged with disorderly conduct.
The three said they wanted to enforce a ban on alcohol on the reservation, where alcoholism is said to be rampant.
"I'm sick of my people dying," Duane Martin, one of the arrested activists, told the Associated Press news agency.
"You've got 18, 19-year-olds trading alcohol for sex."
Four shops outside the reservation sell millions of cans of beer a year, mostly to American Indians, AP says.
Tribal officers drawn from local populations police Native American reservations in the US.
The Oglala Sioux police at Pine Ridge said the searches carried out by the three activists were illegal.
Officers themselves have no right to inspect vehicles without having probable cause to believe a crime has been committed, they say.