"Legislative power" is a distinctly modern conception which presupposes a modern understanding of "law." In medieval Europe the authority of laws was variously attributed to God, nature, or custom; human authorities "found" or "declared" or enforced the law but were not thought to create it. Consequently, medieval jurists did not distinguish "legislative" from "judicial" powers. Through the end of the sixteenth century, the English Parliament (like its continental counterparts) was primarily regarded as a court, an ultimate court of appeal for individuals as well as communities. It was at most an incidental consideration whether Parliament was "representative" because law was not a matter of will but of knowledge.
The modern conception traces the authority of law precisely to the will of the lawmakers. It is this assumption of a pure power to make or unmake the laws that allows for our artificially clear distinction between "legislative" (that is lawmaking) and "judicial" or "executive" (law-applying) powers. In acknowledging law as the creation of particular human wills, the modern view liberates government from encrusted tradition, from folklore and superstition, above all from manipulation by legalistic conjurings. At the same time, however, this view of law opens the chilling prospect of an unlimited coercive power, since the power to create the laws seems, by its very nature, superior to the constraints of law. This sort of reasoning, powerfully advanced by theorists of sovereignty in the seventeenth century, was treated by william blackstone in the next century as virtually self-evident: for any court to declare invalid an act of Parliament, he observed, "were to set the judicial power above that of the legislature, which would be subversive of all government."
The Framers of the American Constitution were nonetheless intent on curbing legislative power. Historians have noted that by the standards of their European contemporaries the constitutional perspective of the American Framers was somewhat archaic, most notably in the Framers' acceptance of a higher law limitation on legislative power and in their indifference to questions about sovereignty or ultimate authority. But in the decisive respect, the concerns and accomplishments of the Framers reflected their quite modern recognition that no laws are simply given, that the scope of legislative assertion is vast and, as the federalist conceded, "the legislative authority necessarily predominates." Thus they set out the legislative powers in the first and longest article of the Constitution, suggesting the primacy of these powers in the governmental scheme and implicitly identifying the reach of the federal government with the reach of its legislative powers. At the same time, the language of Article I emphasizes the open-endedness of legislative power precisely by its focus on the powers rather than the duties, objectives, or obligations of the legislative branch.
Perhaps the most important checks on legislative power in the Constitution are those that seem merely procedural or institutional. In the first place, the Constitution sets up a formidable institutional gauntlet for legislative proposals, requiring that they obtain majorities in each house of Congress and then secure approval from the President (or extraordinary majorities in Congress). The Constitution also seeks to assure some independent authority for the executive branch and the judiciary by removing the selection and tenure of these officers from immediate congressional control. Ultimately, almost all executive and judicial action depends on prior statutory authority and funding from Congress. And it is impossible to say with confidence when a legislative enactment (apart from an actual bill of attainder—imposing criminal sanctions on particular individuals) would be so specific and peremptory as to infringe the essential law-applying authority of the executive or the judiciary. But in practice the institutional reality of the separation of powers usually does preserve a protective screen of independent judgment between the legislative will and the force of law as applied.
Direct limitations on legislative power in the Constitution are perhaps the most dramatic legacy of the Framers' distrust of legislative power, but they are probably not the most efficacious or important. From the outset, Congress has been emboldened to exercise powers beyond those specifically enumerated in Article I, either by construing implied powers or appealing to the requisites of national sovereignty. The Supreme Court sought to give some force to these limitations in the early decades of this century in order to prevent Congress from preempting the legislative authority of the states. But these efforts were repudiated by the Court after the 1930s and the repudiation of judicially enforceable limits has been explicitly reconfirmed in the current era. Even the limitations imposed by the bill of rights on behalf of individual liberty have very rarely been construed by the Supreme Court in ways that threatened federal legislation.
As it has expanded, however, federal legislative power has also been dispersed in striking ways. In recent decades, the federal courts, invoking vague or general constitutional clauses, have assumed the power to impose elaborate requirements on states and localities in a more or less openly legislative (law-creating) manner. Meanwhile, since the 1930s, Congress has delegated more and more legislative power to federal administrative agencies. Though Congress retains the ultimate power to block what courts and agencies do, its passivity may or may not be properly construed as acquiescence. Thus the dispersal of legislative powers seems to threaten the central promise in the modern conception of law—that there is always an identifiable human authority to hold responsible for the law.
Fisher, Louis 1985 Constitutional Conflicts between Congress and the President. Princeton, N.J.: Princeton University Press.