CANNON BALL, N.D. — Protesters trying to stop construction of the Dakota Access oil pipeline are bracing for a confrontation with police Thursday after the demonstrators refused to leave private land in the pipeline’s path.

A months-long dispute over the four-state, $3.8 billion pipeline reached a crisis point when some 200 protesters set up camp on land owned by pipeline developer Energy Transfer Partners. The disputed area is just to the north of a more permanent and larger encampment on federally owned land where hundreds of protesters have camped for months.

Law enforcement officials demanded that the protesters leave the private land on Wednesday, but the protesters refused. It appeared only thick fog and cloudy skies kept a large contingent of law enforcement officers from moving in. Officials have frequently monitored protesters by air.

“At some point the rule of law has to be enforced,” Cass County Sheriff Paul Laney said Wednesday. “We could go down there at any time. We’re trying not to.”