The U.S. Army Corps of Engineers (USACE) ordered protesters to disband their camps in North Dakota Saturday as protesters and law enforcement squared off again over construction of the $3.8 billion Dakota Access oil pipeline.

USACE gave the protesters until Dec. 5 to vacate property near the Cannonball River in south-central North Dakota or face arrest. USACE officials said their decision was aimed at protecting the general public from violent confrontations between protesters and law enforcement officials.

The pipeline’s backers have been stalemated in their efforts to obtain a federal easement to tunnel under a dammed portion of the Missouri River at Lake Oahe, adjacent to the Standing Rock Sioux Tribe reservation. Tribe leaders immediately criticized the USACE for its pronouncement.

Standing Rock Sioux Chairman Dave Archambault II said he was disappointed in the USACE’s decision, but the protesters’ “resolve to protect our water is stronger than ever.”

As tempers again flared and more than 30 arrests were registered, protesters who call themselves “water protectors” traveled to the state capital at Bismarck, staging demonstrations at a shopping mall and drawing the intervention of local police. Last week, violence broke out when protesters tried to cross a bridge near the reservation that has been blocked by law enforcement.

“Heavily weaponized and undercover, police physically assaulted and arrested close to 50 protectors within minutes of their gathering peacefully,” a Sioux tribe spokesperson told local news media. Backers of the pipeline described a different scene, including “reports of protesters” use of improvised explosive devices [putting] the lives of law enforcement peacekeepers as well as protesters in peril.”

Activists have reportedly destroyed construction equipment as part of the protests, and the Morton County, ND, Sheriff’s Office said it has made more than 500 arrests in the past month.

As national news media attention increasingly focused on the standoff, Native American opponents have made it clear that they see this pipeline fight as part of a historic continuum of broken treaties and promises by the U.S. government. The Sioux, also known as the Lakota, view the early 1960s creation of the Oahe Dam in South Dakota, which formed a 250-mile-long upstream lake, as another intrusion and indignity by the federal government.

As theObama administration continues to postpone a decision, efforts on both sides have stiffened with the courts and federal regulators poised for decisions.

A spokesperson for a coalition backing the pipeline, the Midwest Alliance for Infrastructure Now (MAIN), expressed concerns about “escalating violence at Cannon Ball that is a direct result of the [Obama] administration’s delay in issuing the final, already-approved easement for work abutting Lake Oahe.”

News reports indicated that the Standing Rock Sioux’s new water intake is set to open later this year as the result of a $30 million grant the tribe received from the American Recovery and Reinvestment Act of 2009. The intake will be 70 miles south of the Dakota Access pipeline. According to MAIN, the new water intake location is located less than two miles downstream from a rail line that carries as many as 700 oil tank cars a day (300,000 b/d) over the Missouri River.