That threat is being taken seriously, and activists are pushing back against it. Members of the tribes have been arrested for protesting against the pipeline, as have allies such as actress Shailene Woodley, a star of the recent Oliver Stone film “Snowden” and the “Divergent” movies.

But Kemble’s arrest is particularly striking as she was not protesting. She was present as a legal observer, wearing a hat that identified her as such. She said she was filming the police per legal observer guidelines. “I wasn’t protesting. I was (serving as a legal observer),” Kemble told the State Journal. “I was targeted by law enforcement for my camera.”

The camera was seized and Kemble was taken to the Morton County jail, where she was held until bond was posted. North Dakota authorities say the city official could face charges of resisting arrest, misdemeanor criminal trespassing, destruction of evidence, and engaging in a riot.

Kemble said she plans to fight the charges, and disputed the talk of a “riot” as absurd. “What alternative universe was the sheriff in that day?” she asked. “It was so peaceful. The whole day was steeped in prayer and ceremony. … The police are fear-mongering.”