As we all know, two years ago, Chief Justice John Roberts changed the Affordable Care Act’s individual mandate into a tax and thus rescued President Obama’s signature legislation. What you may not know is that with this slight of hand—or flick of the wrist—he actually sent Obamacare flying from the constitutional frying pan into the constitutional fire.

That is, if you accept the Great Alchemist’s transmogrification of a penalty-enforced regulation into a mere tax on the condition of not owning health insurance—in other words, a “unicorn tax,” a creature of no known provenance that will never be seen again—if you accept that, you torque up the ACA’s constitutional tension vis-à-vis the Origination Clause.

Article I, Section 7, Clause 1 says: “All bills for raising revenue shall originate in the House of Representatives; but the Senate may propose or concur with amendments as on other bills.” This clause was put in to ensure that that most awesome federal power was lodged in the political body most sensitive to public opinion.

“The power to tax is the power to destroy,” John Marshall wrote in the foundational 1819 case of McCulloch v. Maryland, so the Framers wanted to ensure that any such destruction came from the people themselves.

Fast forward to December 2009, immediately before the ur-Tea Party state of Massachusetts expressed the nation’s displeasure with Obamacare by electing a Republican to the Senate. That’s when the Senate took a bill giving benefits to members of the military who were first-time homebuyers and, as George Will put it recently, “‘amended’ this bill by obliterating it.” Harry Reid renamed it and replaced its entire contents with the ACA.

While the Origination Clause doesn’t apply to situations where the Senate creates a government program and then institutes taxes to pay specifically for that program, the Obamacare tax isn’t earmarked to pay for anything in particular. Similarly, taxes that are “analogous to fines” are exempt from the clause’s requirements, in that they enforce compliance with a law passed under one of Congress’s other enumerated powers—not the taxing power—but John Roberts foreclosed that interpretive option here.

Of course, the Senate can amend House-passed revenue bills, but only if the amendment is “germane” to that bill’s subject matter. That loophole has turned out to be wide enough for the Kentucky Derby to be run through, but still what was done with Obamacare was breathtakingly unprecedented: If a bill to fundamentally restructure the national health care system is a germane amendment to a bill regarding housing tax credits for servicemen, then the word “germane” has no meaning. (I’m reminded of that great line from Princess Bride, best read in a vaguely Spanish accent: “You keep using that word. I do not think it means what you think it means.”)

Finally, Obamacare’s defenders argue that the Obamacare tax isn’t a tax because its purpose isn’t to raise revenue but instead to encourage certain behavior. (I guess that means it’s no longer a Roberts unicorn tax but instead a Schrodinger’s cat tax.) But if any tax with a behavior-changing purpose or effect—so, all of them—were exempt from the Origination Clause, then that’s one more liberty-protecting clause that’s read out of the Constitution.

In any event, all of these arguments were made to the U.S. Court of Appeals for the D.C. Circuit last week by Pacific Legal Foundation attorney Tim Sandefur (also a Cato adjunct scholar, and my friend), in Sissel v. Department of Health & Human Services. This lawsuit was brought by an Iowa artist and small-business owner who neither has nor wants health insurance, preferring to invest his limited resources in his business.

I have no illusions that the hostile judicial panel will enforce this (or any) limitation on federal power — Barack Obama’s gambit to pack the D.C. Circuit is already paying dividends — but Sissel keeps open yet another front in the ideological battle of our time: are we to enforce the Constitution’s structural provisions (which stand in the way of much of the progressive project) or relegate our founding document to the status of a relic under glass that we observe in the breach.

Although President Obama recently declared that the debate over his health care law “is over,” to quote John Belushi, “nothing’s over till we decide it is.” It should be no surprise that a law forced on the American people against their will is still unpopular, or that its implementation continues to hit snags—you can only defy basic economic laws and human nature for so long—and this isn’t the last we’ll hear of lawsuits against it. Stay tuned.

For more details on the Origination Clause arguments against Obamacare, watch this recent Cato forum; my opening remarks there served as the basis for this article.