Proposed oil and gas pipelines have faced a myriad of legal challenges in the past several years. Even where pipeline proponents have prevailed, the cost and delay of protracted litigation has often caused cancellation of pipeline projects. In addition, presidential transitions have led to abrupt reversals of pipeline policies, which courts have often reviewed skeptically. This Article explores the regulatory framework for pipeline construction and analyzes recent lawsuits, describing the legal requirements that agencies must follow to change policies and discussing policies of the Obama and Trump Administrations in context of the legal challenges. It concludes by analyzing the approaches taken by pipeline opponents and discussing implications for future projects.