NEW YORK (Reuters) – A U.S. appeals court on Friday denied Dakota Access LLC’s petition for a rehearing on a court decision to cancel a key permit for its oil pipeline, court documents show.

The decision by the United States Court of Appeals for the District of Columbia means the Dakota Access Pipeline (DAPL) technically is still trespassing on federal land because it does not have a permit to cross under South Dakota’s Lake Oahe. The environmental review of the line is continuing, and is not expected to be completed until March 2022.

The 570,000 barrel-per-day DAPL began operating in mid-2017 but drew controversy during construction as Native American tribes and activists protested its route under Oahe, a critical drinking water source for the tribes.

DAPL is the largest pipeline out of the Bakken region, which produces about 1 million barrels of crude per day in North Dakota and eastern Montana. If the pipeline were forced to close, the state of North Dakota estimates production could fall by 400,000 bpd temporarily.

Last summer, a U.S. district court judge threw out a federal permit for the line to operate under the lake and ordered an environmental review for that section of the pipeline. A three-judge panel at the circuit court in January upheld the lower court’s decision to vacate the permit and require the review.

The pipeline’s operators wanted the circuit court to reconsider the panel’s decision.

“This marks the complete end of the appeals court proceedings on this case,” said attorney Jeffrey Rasmussen, of Patterson Earnhart Real Bird & Wilson LLP, which represents the Yankton Sioux Tribe in the case.

It is possible, however, that Dakota Access could petition the U.S. Supreme Court to keep the line running.

A spokeswoman for Energy Transfer LP, DAPL’s majority owner, declined to comment on current or pending legal matters.

(Reporting by Laila Kearney and Devika Krishna Kumar; Editing by Dan Grebler)