Oil pipelines are no strangers to controversy, often courting a wide range of opposing opinions: Witness the years of debate that plagued the Keystone XL project between the United States and Canada, eventually blocked by US President Obama in November 2015.

The latest project to attract the ire of protesters, a 1,100-mile pipeline already under construction, is set to pass through four US states – Iowa, Illinois, North Dakota, and South Dakota. Its aim is to transport Bakken Shale oil from North Dakota directly to US Gulf Coast refineries, the first pipeline to do so.

The core group of opposition is the native American Standing Rock Sioux Tribe, which says the pipeline could disturb sacred sites, as well as contaminate water for millions of people. They have been joined by activists from dozens of different tribes, and the protest, which began in April, now boasts upward of 1,000 indigenous participants.

"The things that have happened to tribal nations across this nation have been unjust and unfair, and this has come to a point where we can no longer pay the costs for this nation's well-being," Dave Archambault, chair of the Standing Rock Sioux Tribe, told Democracy Now last week. "All too often we share similar concerns, similar wrongdoings to us, so we are uniting, and we're standing up, and we're saying, 'No more.' "

The protests have temporarily shut down construction, and about 30 people have been arrested in recent weeks. The group behind the pipeline, Dakota Access, filed a restraining order against Mr. Archambault and other protesters earlier this month in federal court; the tribe subsequently sought a preliminary injunction to halt construction.

As legal proceedings unfolded over the $3.7 billion project last week in the US District Court for the District of Columbia, about 100 members of the native American group protested outside. They were joined by actors Susan Sarandon, Riley Keough, and Shailene Woodley.

"I'm here as a mother and a grandmother," said Ms. Sarandon, an Oscar-winning actress known for social and political activism, "to thank the people of the Standing Rock community for bringing our attention to this horrible thing that is happening to their land, which in turn will endanger all of us... because all of our waters are connected."

As part of their legal case, the protesters say the US Army Corps of Engineers violated historic preservation and environmental laws by giving the pipeline their approval. Supporters counter that the project would, in fact, provide safer and cheaper passage for the Bakken oil, when compared with road or rail transport.

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District Court Judge James Boasberg is expected to announce his decision on the preliminary injunction requested by the tribe no later than Sept. 9.

This report contains material from Reuters and the Associated Press.