The coalition of groups that opposed the Dakota Access pipeline are looking to tie up its fate for months or even years if President-elect Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE seeks to undo the Obama administration’s decision Sunday to withhold an easement for its construction.

Tribal groups and environmental activists cheered the Army Corps of Engineers' decision to reject a construction permit for the pipeline’s route across the Missouri River and instead conduct an environmental impact assessment of the project.

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It represented a huge victory for protesters who had set up a large and growing camp near the Standing Rock Sioux reservation, but they separately signaled they are digging in for a longer fight.

An Environmental Impact Statement (EIS) could take years to execute, meaning the move would delay the pipeline indefinitely.

And while Trump could move to undo the EIS, groups opposed to the pipeline said this would trigger a legal fight that could tie up the project on its own.

Jan Hasselman, an Earthjustice lawyer who represents Standing Rock in its lawsuit against the project, said any Trump move is “subject to judicial review” and that the tribe is planning to sue.

Pipeline foes acknowledged the Army Corps’ decision was not the end of the Dakota Access fight, vowing to resist any effort to undo it, a strategy that carries the promise of renewed public pressure against Trump.

In a Monday statement, Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.), an early Standing Rock supporter, said out-of-power progressives should look to protest Trump actions more aggressively.

“These are lessons that must not be lost as we enter the Trump era,” he said. “It is a time for being smart and going forward in building a strong and victorious grassroots movement.”

Rep. Raul Grijalva (D-Ariz.), the top Democrat on the Natural Resources Committee, said this “big win for tribal rights, for environmental quality and for every American who has stood in solidarity with the water protectors” should survive after Obama leaves office.

“It now falls to the Trump administration to follow the law, treat this entire process with the respect and seriousness it demands, and honor the sacrifices of the Americans who put themselves in harm’s way to demand justice at Standing Rock,” Grijalva said.

The Obama administration’s decision puts an early, high-profile decision on President-elect Donald Trump’s desk.

Industry groups that support the project are pushing Trump to move quickly to approve the project and plan to redouble their outreach efforts as his inauguration gets closer.

Trump has backed the pipeline, something his transition team reiterated on Monday.

“That’s something we support construction of, and will review the full situation in the White House and make an appropriate determination at that time,” Trump spokesman Jason Miller said Monday.

Trump’s team confirmed his support for the project last week, with the campaign releasing a memo to supporters saying he would “cut the bureaucratic red tape put in place by the Obama administration that has prevented our country from diversifying our energy portfolio.”

Industry backers said approving Dakota Access should be a top priority for Trump.

“I am hopeful President-elect Trump will reject the Obama administration’s shameful actions to deny this vital energy project, restore the rule of law in the regulatory process, and make this project’s approval a top priority as he takes office in January,” American Petroleum Institute President Jack Gerard said in a Sunday statement.

Locally, North Dakota Petroleum Council President Ron Ness said the group “looks forward to the enforcement of the rule of law and the approval of an easement by the incoming Trump Administration.”

Trump has long supported increasing fossil fuel development in the United States and said he would approve energy projects like the Keystone XL pipeline as president. An order supporting Dakota Access would fit within that platform and be an early indication about how aggressive he intends to be when it comes to energy projects.

A ClearView Energy memo published Sunday suggested Trump officials could step in and undo Sunday’s order, or a GOP-controlled Congress could stop the effort legislatively.

Standing Rock Sioux Chairman Dave Archambault on Monday told Reuters he hopes to meet with Trump officials and convince them to maintain Obama’s approach to the pipeline.

“The current administration did the right thing, and we need to educate the incoming administration and help them understand the right decision was made,” he said.