North Dakota Gov. Jack Dalrymple ordered Dakota Access Pipeline protesters Monday to immediately evacuate the main camp they’ve maintained on federal land for months because of “severe winter weather.”

Snowfall, which began blanketing the region Monday, is expected to stop on Wednesday, according to a winter storm warning from the National Weather Service.

The Republican governor, however, ordered the protesters not to return.

“Winter conditions have the potential to endanger human life, especially when they are exposed to those conditions without proper shelter, dwellings or sanitation for prolonged periods of time,” Dalrymple’s order said. “These persons are ordered to leave the evacuation area immediately, and are further ordered not to return to the evacuation area.”

Stephanie Keith / Reuters Snow blankets the Oceti Sakowin camp, site of protests against construction of the Dakota Access Pipeline near the Standing Rock Indian Reservation near Cannon Ball, North Dakota.

Protesters, who call themselves water protectors, who violate the order “[do] so at their own risk, and assume any and all corresponding liabilities for their unlawful presence and occupation of the evacuation area,” Dalrymple said.

Standing Rock Sioux Tribal Chairman Dave Archambault said late Monday: “This state executive order is a menacing action meant to cause fear, and is a blatant attempt by the state and local officials to usurp and circumvent federal authority.”

Members of the Standing Rock Sioux tribe and their allies, sometimes numbering in the thousands, have camped in tents, yurts, tipis and other makeshift lodgings on federal land near the pipeline’s route.

A coordinator at the Standing Rock Medic and Healer Council, which runs medical and other services at the sprawling Oceti Sakowin camp and others, told The Guardian that they are prepared to continue providing care without government assistance.

The evacuation order came after the U.S. Army Corps of Engineers, which has oversight of the camp area, announced Friday that it would close the area to the public on Dec. 5.

The Army Corps softened its stance Sunday by saying it “has no plans for forcible removal” of protesters who disobey the deadline to leave. Overstaying the cutoff carries legal risks, however, as the Army Corps warned that protesters could be punished for violating federal, state or local laws.

The Standing Rock Sioux had quickly vowed to disobey the Corps’ deadline to leave.

The Oceti Sakowin camp is the main base for protesters who oppose the 1,172-mile pipeline, which begins in North Dakota and crosses through South Dakota and Iowa on its way to Illinois.

Safety concerns also prompted the Army Crops’ decision last week to ban people from the area, Col. John Henderson, district commander of the Army Corps, said in a letter to Archambault last week.

Recent clashes between protesters and police have become more violent, and the onset of North Dakota’s harsh winter will make it tough to deliver emergency services to anyone north of the Cannonball River, Henderson wrote.

The Army Corps had encouraged the Sioux and its allies to relocate to a “free speech zone” for peaceful protest on the other bank of the Cannonball River, which is more accessible for police, fire and medical services.

“We fully support the rights of all Americans to exercise free speech and peacefully assemble, and we ask that they do it in a way that does not also endanger themselves or others, or infringe on others’ rights,” Henderson said.

Perhaps the most serious confrontation occurred last week when a woman was hit with an explosive device that witnesses said was thrown at her by police. Sophia Wilansky, 21, may lose her arm, her father said last week.

The presence of protesters also interferes with a rancher’s grazing rights, according to Henderson.

Morton County Sheriff Kyle Kirchmeier, whose office has arrested more than 500 protesters, had criticized the Army Corps for backing off.

The Army Corps “is basically kicking the can down the road, and all it is doing is taking the liability from the Corps and putting it on” the Standing Rock Sioux tribe, he told the Associated Press.

The $3.8 billion privately built pipeline is largely complete except for a 20-mile section that would cross beneath Lake Oahe near the Standing Rock Sioux’s reservation. The tribe has sought to block its completion, saying that the Army Corps did not conduct a proper environmental review of its impact.

The Obama administration will not grant a permit for the disputed section to Energy Transfer Partners, the developer, until a review of the tribe’s concerns that began in September is completed.