The decision to advance the pipelines cast aside efforts by President Barack Obama's administration to block construction of the two pipelines, while making good on one of Trump's campaign promises.
As he signed the documents Tuesday in the Oval Office, Trump also vowed to "renegotiate some of the terms" of the Keystone bill and said he would then seek to "get that pipeline built."
Trump also issued executive actions declaring oil pipelines constructed in the US should be built with US materials, streamlining the regulatory process for pipeline construction and shortening the environmental review process.
Trump during his campaign said he would streamline the approval of the Keystone XL pipeline, which was stalled for years in the Obama administration until Obama denied approval for the pipeline's construction altogether in November 2015.
And Trump said for the first time in December that he supported construction of the Dakota Access Pipeline, which stalled last year amid protests opposing its construction on Native American lands. The Obama administration denied the company a permit it needed to complete the pipeline late last year.
Protesters of the pipeline projects quickly condemned the decisions Tuesday.
"President Trump is legally required to honor our treaty rights and provide a fair and reasonable pipeline process," said Standing Rock Sioux Tribe chairman Dave Archambault II in a statement. "Americans know this pipeline was unfairly rerouted towards our nation and without our consent. The existing pipeline route risks infringing on our treaty rights, contaminating our water and the water of 17 million Americans downstream."
Environmental groups and activists were also quick to slam the decision, with Tom Steyer, the president of NextGen Climate, accusing the Trump administration of putting "corporate interests ahead of American interests."
"The pipelines are all risk and no reward, allowing corporate polluters to transport oil through our country to be sold on the global market, while putting our air and water at serious risk," he said in a statement.
Meanwhile, Sen. Heidi Heitkamp, a Democrat from North Dakota where the Dakota Access Pipeline is being built, welcomed the move, as did Sen. Joe Manchin, a Democrat from West Virginia.
"What this country needs is more jobs, and that is why I have always been a proponent of the Keystone XL Pipeline and was an original cosponsor of legislation approving the Keystone XL Pipeline project," Manchin, who has already supported several of Trump's nominees and initiatives, said in a statement. "With a majority of Americans in support of the Keystone XL pipeline's construction, I'm glad we are finally moving forward with this important project."
Just as Trump on Tuesday flicked to the need to "renegotiate" the Keystone XL pipeline terms, Trump during his campaign argued not just for quick approval of the pipeline, which would shuttle oil from Canada to the Gulf of Mexico, but also said he would push for a deal that would grant US taxpayers a share of the profits. Trump said that the US would approve the pipeline while also seeking a "better deal."
Trump's approval of both pipelines are early signs of how his administration will take a drastically different approach to energy and environmental issues. Beyond approving the pipelines, Trump has also vowed to slash environmental protection regulations and has nominated several skeptics of the overwhelming scientific consensus on climate change to key Cabinet posts dealing with environmental issues.
New wave of protests expected
Environmental groups and their progressive allies have already begun to mobilize against Trump's directive.
The Indigenous Environmental Network, a leading tribal organization dedicated to blocking further construction of the Dakota Access project, promised a new round of "massive mobilization and civil disobedience."
The documents signed by Trump are online now
but were not provided directly to the tribes or their legal advocates.
Earthjustice, a nonprofit environmental law organization that represents the Standing Rock Sioux Tribe, told CNN they were prepared to act if Trump seeks to cut off the environmental review ordered by the Obama administration in December.
"Nothing in the Presidential Memorandum changes that or even addresses (that decision)," lead attorney Jan Hasselman said in an email. "If the Corps responds to this directive by issuing the easement without the (Environmental Impact Statement) process, it will be violating the law and subjecting itself to additional litigation."
The tribe does not plan to launch legal action against Tuesday's directive, which asks for the Army Corps of Engineers to "review and approve" the final steps in the construction process "in an expedited manner" -- but not to circumvent the ongoing review.
Energy Transfer Partners, the company building the pipeline, needs an easement -- or legal permission -- from the Army Corps of Engineers to drill under Lake Oahe -- about a half-mile upstream from the Standing Rock tribe reservation border -- to complete the project.
The headsman council at the Oceti Sakowin camp, home to a large protest site during demonstrations last year, issued a call on Tuesday for "allies and people to stand up where they are" and engage in "mass civil disobedience as a showing of solidarity for Standing Rock."
Desiree Kane, who spent seven months at the Oceti Sakowin Camp as a media volunteer, told CNN she ready to answer the call.
"I leave tomorrow morning," she said in an email.
Organizers from 350.org, the Sierra Club, CREDO, and other groups have already planned a rally outside the White House at 5 p.m. Tuesday to protest the decision.
"The Keystone XL and Dakota Access pipelines would be a disaster for the land and water, the rights of Indigenous peoples, and the climate," they said in a statement.
"Both pipelines ignited widespread grassroots resistance worldwide, and Trump's executive orders are renewing mass opposition to the projects."