LAST NOVEMBER, on the day that voters were electing the most anti-Washington Congress since before the New Deal, the Supreme Court was hearing oral argument in United States v. Lopez, a case that questioned the very foundations of the post-New Deal world. Conventional wisdom was stunned by the results of the November election. It was shocked again late last month when the court handed down its decision in Lopez.

Could the New Deal be on the ropes not only in the political but in the legal arena as well? Not yet, but the potential is there.

In 1992, Alfonso Lopez, a 12th-grade student living in San Antonio, Tex., brought a handgun to school in violation of the Gun-Free School Zones Act Congress had passed in 1990. Although Texas law already banned having a gun at school, Lopez was charged under the federal statute. Rather than treat this as a gun-control case, however, Lopez's public defender asked a simple question: Where did Congress find its authority to enact the statute?

A question of that kind is so rare today as to be all but impertinent. Yet there it was. After the Court of Appeals for the 5th Circuit found for Lopez -- Judge William L. Garwood reminding federal attorneys that the Constitution "establishes a national government of limited and enumerated powers" -- the Supreme Court agreed to hear the case. When all the dust had settled, the high court too agreed with Lopez: Congress in fact did not have authority to pass the statute.

Notwithstanding comments from the losing side, from President Clinton on down, Lopez is thus not about guns or school safety or even states rights. It is about authority. And that, precisely, is what has jarred official Washington. Indeed, the case raises the most basic questions in politics: Where does government get its authority, and what is the scope of that authority? Those questions have hardly been asked since the New Deal.

In fact, when it enacted the statute, Congress never even bothered to cite the source of its authority. Much later, after the government lost in the 5th Circuit, Congress patched together a quick, retrospective rationale, invoking the Constitution's tried-and-true commerce clause -- the power of Congress "to regulate commerce among the several states." Through that single power, Congress has brought about the vast regulatory state we know today, mostly since the New Deal.

Thus, if the commerce power is less robust than we thought -- which is what the court said for the first time in nearly 60 years -- the constitutional foundations of the modern regulatory state are in jeopardy. For a nation that prides itself on constitutional government, that is no small matter.

Just to be clear, the court stopped well short of declaring modern commerce-clause regulation unconstitutional. In fact, as Justice Clarence Thomas made clear plain in his trenchant concurrence, the court still has a very ample view of the commerce clause -- a view utterly at odds with the court's limited-government premise. Sooner or later, therefore, the court is going to have to come to grips with that inconsistency. The nub of the matter is found in the court's premise, which is nothing less than the Constitution's premise. Chief Justice William Rehnquist, writing for the majority in Lopez, put it simply: "We start with first principles. The Constitution creates a Federal Government of enumerated powers."

In America, legal power arises from the people. More precisely, the Constitution establishes a government of delegated, enumerated and thus limited powers. Power is delegated by the founding generation (that makes it legitimate); enumerated in the Constitution (that makes it legal); and limited by virtue of that delegation and enumeration.

Students of the Constitution -- and of "The Federalist Papers" in particular -- know full well that without that foundation our system is shorn of any pretense of legitimacy. To be sure, succeeding generations can amend the Constitution, adding or subtracting powers. But to be legitimate, power must first be authorized. Otherwise it is illegal.

The problem of illegitimacy arose in spades during the New Deal, of course, when Congress and the executive undertook programs that were in no way authorized by the Constitution as it had been interpreted for the previous 150 years. President Roosevelt acknowledged as much in 1935 in a letter to the chairman of the House Ways and Means Committee: "I hope your committee will not permit doubts as to constitutionality, however reasonable, to block the suggested legislation."

When the court found that the New Deal Congress had indeed gone beyond its authority, rather than try to expand that authority through constitutional amendment, Roosevelt threatened to pack the court with six addition members. There followed the famous "switch in time that saved nine:" the court reinterpreted the commerce clause in the 1937 Jones & Laughlin case and the modern regulatory state poured through the opening, all without benefit of constitutional amendment.

Although many historians have pointed to a recalcitrant, reactionary court as the source of the problem, that view today is increasingly challenged. Indeed, it was undercut in 1968 by no less than Rexford Tugwell, one of the New Deal's principal architects: "To the extent that {our policies} developed, they were tortured interpretations of a document intended to prevent them."

Yet in the three dissents in Lopez, we find just such "tortured interpretations," with Justice David Souter going so far as to speak of "the untenable jurisprudence from which the court extracted itself almost 60 years ago." One imagines our first 150 years to have been one grand jurisprudential mistake.

Indeed, in not one of the dissents -- nor even in the concurrence by Justice Anthony Kennedy, joined by Justice Sandra Day O'Connor -- do we find even a mention of enumerated powers. It is as if the Constitution arose, Phoenix-like, in 1937, with the court thereafter playing interpretive handmaiden to the political branches, finding powers that are nowhere enumerated in the document.

But the majority itself is not immune from the charge of "activism" in finding powers nowhere granted, as Thomas alone plainly sees. For the post-New Deal rule it leaves in place -- whereby Congress has power to regulate anything that "substantially affects" interstate commerce -- is not only inconsistent with the terms and purpose of the commerce clause but effectively guts the doctrine of enumerated powers, the very premise of the Constitution.

As Thomas notes, if this single power of Congress were so vast, what was the point of having enumerated Congress's other powers? The dissent's reading of the commerce clause is boundless, he concludes, but the majority's reading is little better. Where does this leave us constitutionally? In declaring that Congress's power to regulate interstate commerce is not a power to regulate everything, the court took the occasion to reassert our founding principle of limited government. This far down the regulatory road that is no small matter. At the least, it is a benchmark to which Congress itself can repair, following November's election, as it tries to re-limit government politically. But unless the court is more prepared than it appears to be in Lopez to develop a principled theory of the commerce power, it may be some time before our government is again limited constitutionally.

Thus, one reading of Lopez is this: We, the court, cannot do it alone. The political branches, through the extra-constitutional court-packing threat of 1937, pressured us into this untenable jurisprudence. Now let them bail us out by re-limiting their own power, thus giving us a green light to reassert candidly the full reach of the constitutional principles of limited government. If the election of last November was a true reflection of the wish of the American people to relimit their government, it may turn out to have had not only political but constitutional implications as well. Roger Pilon directs the Center for Constitutional Studies at the Cato Institute.