Let us set aside the environmental issue of whether or not the extraction of oil sands is too dirty, and too energy intensive a process, to make sense. If Canada wants to extract petroleum in such a fashion, that is their business.
The question the President faced was whether or not to build a new pipeline to bring the oil so extracted to refineries on the Gulf Coast. That proposed pipeline would have passed through what is known as the Ogallala Aquifer, which supplies water to much of the Great Plains. One accident, and the result could be devastating. Ask yourselves this: Do you like grabbing a burger at McDonald's every once in awhile? A poisoned aquifer could result in no corn, and no corn means no beef, and no beef means no burgers.
Earlier, the Obama adminsitration had asked the company that wishes to build the pipeline to come up with a different route. The Republicans in Congress wanted to short-circuit that process for political gain. I am sure that President Obama entertained political calculations of his own. But, nonetheless, he made the right decision not to be rushed into approving a dangerous pipeline, when a few more months might allow the company to come up with a new route that would not endanger the Ogallala Aquifer.
The approval process has already taken three years and the administration might do well to acknowledge that we need to find ways to expedite these requests. Time waits for no man, nor for the EPA. And, could someone explain to me why we can't build a refinery in northern Minnesota, along the Great Lakes, and refine the oil there?