Trans Canada (a Canadian company) applied to the U.S. Department of State for a permit to cross the U.S.-Canada International border with the Keystone XL pipeline project in 2008. If constructed, the pipeline would carry crude oil produced from the oil sands regions of Alberta, Canada, to U.S. Gulf Coast refineries. Because the pipeline would connect the United States with a foreign country, it requires a Presidential Permit issued by the State Department. Issuance of a Presidential Permit requires a finding that the project would serve the "national interest." This book describes the Keystone XL pipeline proposal and the process required for federal approval. It summarizes key arguments for and against the pipeline put forth by the pipeline’s developers, federal agencies, environmental groups, and other stakeholders. Also discussed is the constitutional basis for the State Department’s authority to issue a Presidential Permit, and opponents’ possible challenges to this authority.