Amnesty International USA is asking the state of North Dakota to address alleged human rights violations against Dakota Access pipeline opponents.
Hundreds of protesters were arrested from August through February. Amnesty International says it has documented numerous instances of excessive force or intimidation by police and excessive criminal charges.
The organization sent a letter asking Republican Gov. Doug Burgum and Attorney General Wayne Stenehjem to drop or consider dropping charges against protesters. The letter also asks them to review police practices and open independent investigations into several cases.
Police have defended their practices, which have included water sprays, tear gas and non-lethal ammunition such as rubber bullets. Police have said some protesters were violent and took part in riots, and that some targeted police both professionally and personally.
This comes on the same day that a federal judge refused to head off the imminent flow of oil in the disputed Dakota Access pipeline.
Judge James Boasberg on Tuesday denied a request by the Standing Rock and Cheyenne River Sioux to stop oil from flowing while they appeal his earlier decision allowing pipeline construction to finish.
Boasberg says a "critical factor" is the tribes' appeal is unlikely to succeed. They say the pipeline violates their religious rights because it's running under a lake they consider sacred. Boasberg says the argument was made too late and is of questionable merit.