The hotly contested Keystone XL and
The projects have become among the country's most potent symbols of the clash between an oil and gas industry seeking to maintain the old order of energy production and the climate change movement pushing for a different direction.
Trump used the two proposed pipelines to send an unmistakable message during his first week in office: energy firms and their projects are back in favor.
When the Obama administration rejected Keystone in 2015 after years of protests and tens of millions of dollars spent by all sides, green-energy champions celebrated a seminal victory. The decision against the project came right before Obama signed a landmark global warming accord with dozens of other heads of state at a summit in Paris.
The Dakota Access project more recently became a national rallying point not only for environmental groups but for Native American tribes who said it threatened grounds they hold sacred. The Standing Rock Sioux Tribe has set up a camp to protest the pipeline, and the battle over it has become violent at times, with protesters clashing with police.
As the fight drew increasing national attention last year, the Obama administration dealt the project a potentially devastating blow that once again sent a strong message of opposition to fossil fuel projects. The U.S. Army Corps of Engineers denied the pipeline a crucial easement and announced it would look for alternatives to its planned route under a dammed section of the Missouri River called Lake Oahe.
Days before Obama's term ended, the Corps of Engineers announced it would start an extensive environmental review that could add months — potentially years — to the permitting process and open the project to more public comment, creating new opportunities for opponents to block it.
Trump's decision to revive the prospects for both projects comes as his administration jettisons much of Obama's climate policy — including U.S. participation in the Paris accord — and promises to work aggressively to curb regulations that inhibit drilling and mining.
As the Trump administration moves swiftly to change direction, it also issued a gag order to the staff at the Environmental Protection Agency, which took a lead in Obama's climate fight. Officials at the agency have been instructed not to interact at all with the news media and to freeze all contracts and grants.
Trump's directives on the pipelines may pay political dividends. The angry opposition to the announcements comes mostly from places and groups that have never supported Trump. By contrast, the moves are likely to be well received by workers in Rust Belt communities who backed Trump in the election and now see him delivering on his promise to work for more jobs in middle America.
The decision on the Dakota Access pipeline instructed the Corps of Engineers to "consider" whether it can grant final approval for the project. It does not immediately clear the way for construction to resume, but strongly tilts in that direction, telling the Corps to consider skipping any additional environmental review.
Jan Hasselman, a lawyer for the advocacy group Earthjustice, called that directive illegal, saying it was "an insult to Standing Rock, and it continues a historic pattern of trampling on the rights of native people."
Environmental groups call the $3.8-billion, 1,170-mile project — nearly all of which has already been built — a threat to clean air and water, as well as to farming communities.
On Keystone, the president emphasized the jobs aspect of the project by insisting that the pipeline be built exclusively with U.S. steel, which he said would generate still more jobs.
That demand may or may not be feasible. If it raises the pipeline's cost, it could prove the death knell for a project that may no longer pencil out financially. The price of oil has plunged over the last couple of years to levels far below what Keystone's designers had envisioned.
The order Trump signed on Tuesday invited TransCanada, the firm that developed Keystone, to submit a new application for a permit for the pipeline. It directed administration agencies to swiftly review that application and issue a new decision within 60 days. That would be in sharp contrast with the nearly eight years during which the project languished before Obama finally rejected it.
During the long delay, fighting Keystone became a rallying point for the environmental movement. While studies showed the effects of the single pipeline on the climate would be negligible — as would be its impact on boosting global oil production — resistance focused on the environmental movement drawing a line in the sand, demanding that public officials stop backing big, invasive infrastructure projects that feed the world's oil habit and undermine the push for more green energy.
TransCanada immediately declared it would seize the new opening for its project, which is designed to ship 800,000 barrels of oil a day from the Canadian tar sands to refineries along the U.S. Gulf Coast.
In a statement, TransCanada vowed the pipeline would create thousands of jobs and boost the American economy, saying it "represents the safest, most environmentally sound way to connect the American economy to an abundant energy resource."
Trump echoed the project's supporters, saying the pipeline could generate 28,000 construction jobs. Opponents dispute that number, saying the new jobs would be less abundant than Trump claims and noting that in any case they would be temporary. They also say the project would undermine the potential creation of many more jobs in solar, wind and geothermal energy.
Trump's directive provoked predictable outrage from environmental groups, which are vowing to mobilize just as they did before to block construction with mass protest and relentless legal challenges.
For all the heavy symbolism, however, the project's impact on the world's energy sector will ultimately be limited.
"In the end, this is all a tempest in a teapot," said Andrew Hoffman, a professor of sustainable enterprise at the University of Michigan. The project, he said, ultimately would not lower prices at the pump or add significantly more greenhouse gases to the atmosphere.
"It is just one more battlefield between the left and the right about free commerce, the role of government and the influence of activists," he said.
Halper reported from Washington and Yardley from Denver.
Follow me: @evanhalper