As thousands of Indigenous activists gather in 90-degree heat at the construction site of the Dakota Access Pipeline at the border of North and South Dakota, North Dakota state officials have shut down highways leading to the site and removed state-owned water tanks that have served as the main supply of drinking water for the encampment, citing public safety concerns.

Estimates of the number of people protesting the pipeline range from 2,000 to 4,000, and 29 people have been arrested over the past two weeks. Though there have been isolated reports of disorderly conduct, trespassing, and interference with observational aircraft, Governor Jack Dalrymple noted that the protests have been largely peaceful.

“Law enforcement has a duty to facilitate the rights to freedom of expression and assembly for those who wish to peacefully protest,” said Tarah Demant, senior campaigner with Amnesty International USA. “International law allows the restriction of the right to freedom of peaceful assembly only if it is carried out for a legitimate aim, such as the protection of public safety. Any restrictions must be proportionate and necessary to meet that aim. Police should be able to maintain public order without repressing protesters’ freedom of expression.”

The pipeline is being built near the Standing Rock Sioux Reservation near Cannon Ball, North Dakota. The protesters claim that the pipeline will infringe on their cultural rights and access to clean water since it will go underneath the Missouri River – the main source of water for the reservation.