"The Trump administration tried to force this dirty pipeline project on the American people, but they can't ignore the threats it would pose to our clean water, our climate, and our communities", Mr Hayes added.
The ruling is a major victory for environmentalist groups that sued to stop the project and for the Native American tribes that have protested against it for years.
If built, it would transport around 830,000 barrels of crude oil per day from Alberta, Canada, and the Bakken Shale Formation in Montana to facilities near Steele City, Neb.
Mr Obama rejected the scheme in 2015 following a recommendation from the Environmental Protection Agency, citing concerns over it increasing USA dependence on fossil fuel.
Trump granted a permit that allowed energy firm TransCanada to build the controversial Keystone XL pipeline shortly after taking office.
No immediate impact in oil markets is seen, as the pipeline isn't scheduled to come online for years regardless of the ruling.
What did the ruling say?
"The department's 2017 conclusory analysis that climate-related impacts from Keystone subsequently would prove inconsequential and its corresponding reliance on this conclusion as a centerpiece of its policy change required the department to provide a 'reasoned explanation, '" Judge Morris said.
"An agency cannot simply disregard contrary or inconvenient factual determinations that it made in the past, any more than it can ignore inconvenient facts when it writes on a blank slate", Morris wrote.
Olivier Giroud does not need to score, says Maurizio Sarri
Giroud told BT Sport: "It's true, I was hoping to score soon because I came back late from the World Cup and lacked a bit of luck. He added: "Today I was in trouble, too". "It's very important because then we can talk again about this competition in February".
AMD shows Zen 2-based 7nm EPYC Rome CPU in action
AMD's Mark Papermaster says the new Zen 2 cores offer double the throughput of Zen and twice the floating point performance. We have 2x performance per socket compared to the previous-gen EPYC processor, and this is an insane leap in performance.
Attorney General Jeff Sessions Resigns
The department confirmed he would be assuming oversight of the Mueller probe from Deputy Attorney General Rod Rosenstein. His recusal was one of his first public acts as attorney-general.
Arsenal held at home by Sporting
And while Nelson may not be a ready-made replacement for Welbeck , Emery says he is keeping a keen eye on his progress. But I think the players were concentrated on the match and we forgot this injury the next minute on the pitch.