He signed executive memorandums paving the way for their construction, but it's not at all clear what this will mean on the ground.
At his final press conference, the president downplayed the importance of climate compared to issues like voting rights and press freedom.
It's not easy.
I-732 would have been a groundbreaking climate policy, but it was opposed not just by big business but by many environmentalists too.
A battle over a ballot initiative in Washington state has boiled over onto the national scene.
Sanders and four other senators sent a letter to Obama asking him to require a full environmental and cultural review of the pipeline.
After Friday's terrorist attacks, activists and organizers are deciding whether to scale back or cancel some planned events.
Is Keystone permanently dead? Will this decision affect the climate? These answers, and more.
The company asked for a delay in review of the pipeline proposal, hoping to push the decision off to the next president. Obama denied the request.