Mr. Obama’s denial of the proposed 1,179-mile pipeline, which would have carried 800,000 barrels a day of carbon-heavy petroleum from the Canadian oil sands to the Gulf Coast, comes as he seeks to build an ambitious legacy on climate change.
Republicans and the oil industry had demanded that the president approve the pipeline, which they said would create jobs and stimulate economic growth. Many Democrats, particularly those in oil-producing states such as North Dakota, also supported the project. In February, congressional Democrats joined with Republicans in sending Mr. Obama a bill to speed approval of the project, but the president vetoed the measure.