On Wednesday, the Fifth Circuit will take another crack at the Affordable Care Act. Commentators on both the left and the right have lambasted the lawsuit, calling it everything from an assault on Americans to of little consequence.

But the constitutional principle at stake in Texas v. United States is far from inconsequential. It involves the very power of the federal government to force people to do something—here, purchase qualifying health insurance. The argument from those on the left—that Congress may use its supposed unenumerated powers to force people to buy this insurance—that is an assault on our democratic principles.

What the Right Gets Wrong

Conservative commentator after commentator has denigrated the most recent challenge to the ACA. These commentators think the lawsuit is trivial and a losing strategy. These criticisms from the right are wrong. The question of whether the individual mandate is still constitutional under the taxing power when it raises no revenue is an important one implicating the fundamental principles of a limited federal government.

In NFIB v. Sebelius, a bare majority of the Supreme Court saved the Affordable Care Act by reinterpreting the individual mandate’s “penalty” as a “tax.” According to that opinion, “the essential feature” of a tax is that “it produces at least some revenue for the Government.”

In the Tax Cuts and Jobs Act of 2017, Congress zeroed out that tax. Congress did not, however, make any other changes to Section 5000A of the ACA.  Subsection (a) still provides that certain individuals “shall . . . ensure” they are covered by “minimum essential coverage.” Because individuals still must “ensure” that they have purchased qualifying insurance, and because the penalty no longer produces any federal revenue, the state plaintiffs have a good argument that the individual mandate is unconstitutional.

Because the individual mandate now raises no revenue, it is missing the “essential feature” of a tax and cannot be supported by the taxing power. To hold otherwise would endorse a broad federal taxing power that would allow the government to do things it otherwise cannot–like force people to buy health insurance–when the “tax” is illusory and raises no government revenue.

It may be that Republican concern with the lawsuit stems from its political unpalatability. Democrats allege (wrongly) that Republicans want to strip health insurance from those with preexisting conditions, and The Wall Street Journal worries that the lawsuit “could blow up politically.” But of course, political expediency is not a judicial argument, nor is it an excuse to dump a lawsuit that raises an important question about the limits of federal power.

Conservative detractors are right to question one thing: the district court’s severability holding. Judge O’Connor held that the individual mandate was so integral to the rest of the statute that the entire ACA must fall if it’s pulled out. But of course severability depends upon congressional intent. Here, Congress itself got rid of the penalty while leaving the rest of the law. This suggests that Congress views the ACA with a zero penalty for the individual mandate as acceptable.

That the individual mandate likely is severable, however, does not make the question of its constitutionality any less important. To uphold the individual mandate as a proper exercise of Congress’s taxing power when the statute raises zero federal revenue removes any discernable limit on the taxing power.

Liberals Are Wrong, Too

Many on the left argue that the individual mandate is constitutional because the current penalty is zero and thus the government doesn’t need to justify the mandate at all. The federal government may rely on its unenumerated powers.

That argument would have the Framers rolling over in their graves. The Constitution establishes a federal government of limited, enumerated powers. As the Supreme Court held in United States v. Sprague, the Tenth Amendment “confirm[ed] the understanding of the people at the time the Constitution was adopted” that “[t]he powers not delegated to the United States by the Constitution … are reserved to the states … or to the people.”

The left’s expansive view of federal power is jaw-dropping: They envision a federal government that may require private individuals to purchase a product based on its unenumerated powers—so long as there is no penalty attached.

The Constitution, on the other hand, says that, in order to act, Congress must employ an enumerated powers — only powers specifically granted to it in the Constitution. Nowhere does the document contemplate a free-floating power to command individuals to buy something. To be sure, the Necessary and Proper Clause gives the federal government additional authority, but only in pursuance of a separate enumerated power.

In short, not only does the left’s argument encourage lawless disregard of federal law, it gets the Constitution backward. The only unenumerated rights contemplated by the Constitution are those reserved to the people in the Ninth Amendment.

The Fifth Circuit Should Reject Both Views

In NFIB v. Sebelius, conservatives consoled themselves with the now-forgotten first half of the opinion which held that Congress may not require individuals to purchase a product under the Commerce Clause. As Justice Antonin Scalia pointed out at oral argument, the government’s claim to do so would allow it to require people to buy broccoli—simply because the government thought it good for them.

The Supreme Court rightly rejected this preposterous argument. And the Fifth Circuit should reject the similarly preposterous argument that the taxing power extends to legislative mandates that raise no governmental revenue. To put not too fine a point on it, a tax that fails to tax anyone is not a tax.