In this land where the people rule, many believe the people’s rulers are out of control. That may change after today’s election. But as the people speak today to the problem of overweening government, the Supreme Court will be hearing a case that could reimpose more lasting restraints on our rulers than anything to come from the polls.

That case, United States vs. Lopez, presents a fundamental question: Is the power of Congress limited only by the guarantees contained in the Bill of Rights, or does the Constitution itself limit Congress by enumerating its powers?

That question may seem of interest only to constitutional scholars, but the implications of the court’s answer are profound and far-reaching. At its writing, the Constitution was a document of enumerated powers, with a vast sea of private liberty reserved. Today, it is a vast sea of powers, lapping at islands of liberty.

The unlikely and unsympathetic case that gives rise to this most basic of questions comes from San Antonio, Texas, where one Alfonso Lopez, a 12th-grade student, brought a handgun to school in violation of the Gun-Free School Zones Act Congress passed in 1990. Although Texas law had long prohibited having a gun at school, Mr. Lopez was charged under the federal law, which prohibits unauthorized individuals from possessing a gun within 1,000 feet of a school.

After losing at trial, Mr. Lopez’s public defender appealed to the 5th U.S. Circuit Court of Appeals, where he found a sympathetic ear in Judge William L. Garwood. Speaking for a three-judge panel, Judge Garwood invoked the Constitution’s principal author, James Madison, to remind federal attorneys that the document “establishes a national government of limited and enumerated powers,” “few and defined,” leaving the rest to the states or to the people, as the 10th Amendment confirms.

But Judge Garwood continued, with language too good to paraphrase: “It is easy to lose sight of all this in a day when Congress appropriates trillion-dollar budgets and regulates myriad aspects of economic and social life. Nevertheless, there are occasions on which we are reminded of this fundamental postulate of our constitutional order. This case presents such an occasion.”

When Congress passed the Act it forgot, it seems, to say just where in the Constitution it was finding its authority. What is worse, even if it had uttered the 20th century’s magic words, “Commerce Clause,” as the government did in court, the power of Congress to regulate commerce among the states would not avail. After all, mere possession — which is what the law prohibited — is not commerce.

That argument would seem unassailable — at least if Madison and company understood the document they drafted. How then have we reached a point where conventional wisdom holds that the decision quickly will be reversed?

To answer that, we need first to appreciate how central the doctrine of enumerated powers was to the original design. Its function was twofold: to legitimize power; then to limit it. To be legitimate, power would have to be “authorized” by delegation from the people. But that very process limited government’s powers to those that were thus authorized and enumerated. So sure were the Federalists of their plan that they resisted the addition of a bill of rights as superfluous: “Why declare that things shall not be done,” asked Alexander Hamilton in Federalist 84, “which there is no power to do?”

But no constitution is self-executing. It takes live people to give life to such a document, people who will or will not be faithful to its larger aims. Thus, in 1794 Madison rose in the House to oppose a welfare bill on constitutional grounds, saying he could not “undertake to lay his finger on that article of the Federal Constitution which granted a right to Congress of expending, on objects of benevolence, the money of their constituents.” Nearly 100 years later, President Cleveland vetoed a bill to buy seeds for drought-stricken farmers on similar grounds — the Constitution enumerated no such power.

Thus it went, for the most part, until the forces of the Progressive era found chinks in the constitutional armor through which to drive their public programs. Chief among those chinks was the Commerce Clause, which had been written, ironically, not to facilitate regulation but to enable Congress to override protectionist regulations that states had passed under the Articles of Confederation. Written thus to enable Congress to “make regular” commerce among the states — much as the court used it in the first great Commerce Clause case, Gibbons vs. Ogden — the clause was seen by Progressives as affording Congress the power to affirmatively “regulate” commerce for all manner of social ends.

Things came to a head in the New Deal, of course, when a frustrated President Franklin Roosevelt threatened to pack six more members onto a court that stood athwart his programs. The scheme failed when the Senate balked, but the court got the message, stepped aside, and the rest is regulatory history — under a government of essentially two-and-one-quarter branches.

Thirty years later, New Deal architect Rexford Tugwell would come clean: “To the extent that these [New Deal policies] developed, they were tortured interpretations of a document intended to prevent them.” How could it be otherwise? After all, if the Framers had meant for Congress to be able to do virtually anything it wanted under the commerce power, why would they have spent so much time defending their doctrine of enumerated powers — or even bothered to enumerate Congress’ other powers?

Today, the legislative water that has poured through the opening the New Deal created engulfs us all, leading many to conclude that it is too late to replug the constitutional dam. That counsel of despair must be resisted. For if the Constitution’s centerpiece of enumerated powers is in fact dead, the Bill of Rights cannot be far behind. Indeed, a Congress with endless unenumerated responsibilities will see to that, as it already has in areas too numerous to count. Today, we should vote, then look for life in the third branch of government.