Note: This article originally appeared at National Review Online on April 5, 2012.

I don’t want to say that the Fifth Circuit’s request to the Obama administration was a stunt, nor that it was trivial. But, alas, it focused on the wrong question.

The president quickly clarified his apparent warning against constitutional review by stating that, of course, he doesn’t question the Court’s powers of judicial review, but he thinks it would be “unprecedented” for the Court to strike down a federal regulation of “economic activity” because it hasn’t done that since the New Deal.

This clarification reveals the real vulnerability in his approach to the Constitution: What exactly does he think Congress does not have the power to do under the Commerce Clause? Or, to be more precise, does the commerce power have judicially enforceable limits – and if so, what are they?

Since Wickard v. Filburn was handed down in 1942, conservatives have been saying that if Congress may regulate any activity which in the “aggregate” has a “substantial effect on interstate commerce,” it may regulate all economic activity – and indeed all activity, period. If so, its commerce power is not limited to the regulation of commerce “among the several States” as the Constitution provides, and is subject only to such limits as may be self-imposed by Congress. And, if that is true, than the commerce power swallows up all the other enumerated powers, and indeed the entire scheme of enumerated powers. Congress is then left to regulate whatever it will, while the powers left to the states or to the people are only those Congress chooses not to regulate, totally reversing the clear meaning of the Tenth Amendment.

In both United States v. Lopez (1995) and United States v. Morrison (2000), the Supreme Court made it clear that the commerce power has some limit, and that non-economic activity (such as criminal conduct) falls outside that limit. The Court has never held that all economic activity is within the commerce power, and although no other result would be consistent with Wickard (which is why Wickard is fatally flawed), allowing Congress to regulate all economic activity would obliterate the distinction that the Court has repeatedly insisted upon between what is national and what is local. As the Court insisted in Morrison, “The Constitution requires a distinction between what is truly national and what is truly local.”

As Justice Scalia said during oral argument on the individual mandate, allowing Congress to regulate virtually all economic activity would violate the “principle that the Federal Government is a government of enumerated powers and the vast majority of powers remain in the States and do not belong to the Federal Government.” Scalia got the Solicitor General to agree on this point, and that was the fatal concession. As Scalia asked, “if the government can do this, what . . . can it not do?” The president obviously thinks that the federal power to regulate commerce “among the several states” is the power to regulate the economy, period. That is why he seems so offended by the prospect of the Supreme Court reasserting that the commerce power does indeed have judicially enforceable limits, but the Court has always insisted that the commerce power is limited. What’s unprecedented is to assert that it’s not limited.

This week the president revealed a major vulnerability in his view of the Constitution, but it was not his apparent attack on the principle of judicial review. It was his very real attack on the principle that the commerce power has a judicially enforceable limit. The reason the Solicitor General had such a rough time during oral argument on the individual mandate is not just that he coughed or was muddle-headed or nervous. It’s that he couldn’t answer Scalia’s question – if the government can force you to buy health insurance, what can’t it force you to do? – and that’s because there is no answer.

The president wouldn’t be able to answer that question any better than his solicitor general. And that’s the right question to ask him, over and over again. That’s where the argument between Solicitor General and the Justices should be elevated into an argument between the president and the American people.