The Keystone XL pipeline should be an open-and-shut case from a climate perspective, the criterion Pres Barack Obama has set for judging it. In a speech in June, he said he would approve the pipeline only if this project does not significantly exacerbate the problem of carbon pollution. By that standard, this should be an easy, data-driven call to make. It hasn't been. The oil industry says Obama should stop stalling. The US Department of State's latest environmental impact report concluded that the Keystone XL pipeline that would transport 700,000 barrels of carbon-heavy tar-sands oil per day from Alberta, Canada, to refineries on the Gulf Coast is unlikely to significantly worsen carbon emissions. But there's a deeper explanation for Obama's caution on Keystone that rarely gets acknowledged. He is the president of a petro state, a country that ranks as an OPEC nation in all but name. And in a petro state, saying no to Big Oil is never easy.