In an amicus, or friend-of-court, brief dated April 8, the U.S. Department of Justice told the Chicago-based 7th U.S. Circuit Court of Appeals that forcing Enbridge to drain portions of its Line 5 pipeline could interrupt service in violation of a 1977 treaty between the U.S. and Canada to keep oil flowing.

The U.S., which is not a party to the case, said the lower court was right to find Enbridge is trespassing on the tribal land, but said the court should reconsider its decision ordering Enbridge to stop operating portions of the pipeline by 2026.

Canada, which is also not a party to the case, had previously argued in an amicus brief that the pipeline should be kept open due to the treaty.

The 2019 lawsuit was filed against Enbridge by the Native American tribe the Bad River Band of Lake Superior Chippewa.

(Reporting by Clark Mindock in New York and Rod Nickel in Winnipeg, Manitoba; Editing by Alexia Garamfalvi and Bill Berkrot)