Abstract: This Foreword argues that the constitutional text favors an approach to both statutory and structural constitutional law that defers, within broad bounds, to congressional authority to determine how to implement constitutional power. In several important contexts, the Constitution grants implementation powers to Congress. These grants include the Necessary and Proper Clause, which provides that Congress shall have the power “[t]o make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers and all other Powers vested by this Constitution in the Government of the United States, or in any Department or Officer thereof.” The upshot of that explicit assignment is not hard to describe. Unless it violates some other provision of the Constitution, when Congress specifies a reasonable means of carrying out its own power or the powers of the coordinate branches, the other branches must respect that decision. This Foreword argues that the Rehnquist and Roberts Courts have given effect to this allocation of implementation power in statutory cases, but not in structural constitutional cases. The Court’s “new textualism” in statutory interpretation builds on a post-New Deal tradition that treated the Necessary and Proper Clause as a broad source of congressional authority to enact odd, and even silly, laws, as long as they satisfied a very minimal threshold of rationality. By enforcing the statutory text, warts and all, textualism enables Congress to use its words reliably to prescribe — and make stick — rough, awkward, and often ill-fitting solutions to complex and contested social problems. In contrast, the Court's “new structuralism” in constitutional law transforms the Necessary and Proper Clause into a delegation of power to the courts to define abstract structural policies. In a novel reading of the clause, both the Rehnquist and Roberts Courts have held that a law is not “proper” if it cannot satisfy the Court's own conception of freestanding principles of federalism and separation of powers. Contrary to the Constitution’s express allocation of implementation power, this approach gives the Court rather than Congress primary responsibility for determining what means are “necessary and proper.”