Congress regularly authorizes and requires administrative agencies to implement and enforce regulatory programs. As such, agencies routinely make decisions about when to promulgate regulations and when to enforce statutory requirements against parties who violate the law. During the 113th Congress, the Obama Administration announced that certain federal agencies would not enforce specific aspects of the Affordable Care Act (ACA) for a period of time in order to allow the public to further prepare for proper compliance with the law in the future. This has led to numerous questions regarding how courts treat administrative delays of regulatory programs. When can a suit be brought to force the agency to apply the law? It is important to distinguish between two distinct types of agency delays: (1) delays resulting from when an agency fails to meet a statutory deadline for promulgating rules or completing particular adjudications, and (2) affirmative decisions to withhold enforcement of a provision of law on the public at large. This book discusses the general legal principles applied in determining whether administrative delays are reviewable in court in these two different contexts and then address whether the procedures outlined in the Administrative Procedure Act (APA) are applicable to these delays.