This chapter surveys current doctrine concerning the scope of Congress’s regulatory, taxing, and spending powers. The Court’s historic pattern of decisions both presents a study in constitutional change and illumines factors that sometimes make change difficult. Prior to the Great Depression and the New Deal, the Court struggled uncertainly to cabin Congress’s powers under Article I. But the Court, seemingly in response to political pressures, substantially abandoned that effort in 1937, when it began to interpret the Commerce Clause as giving Congress vast powers to regulate the national economy and the Taxing and Spending Clause as allowing it to create largesse-dispensing programs that the Founding generation could not have imagined. At least since the 1980s, a strain of conservative scholarship has maintained that the modern, swollen national government finds no justification in the original Constitution and that the Court should enforce the original design. This chapter traces the Court’s limited success in implementing a course correction and identifies the considerations that have given pause to conservative justices. It also describes the Court’s more aggressive efforts to limit congressional power under the Thirteenth, Fourteenth, and Fifteenth Amendments, all of which include express authorizations of Congress to “enforce” their substantive guarantees.