Last April, after multiple days of Supreme Court arguments in the Obamacare case, I wrote about the Obama administration’s incoherent defense of its signature legislation.

Obamacare, officially called the Patient Protection and Affordable Care Act, represents an extravagant exercise of federal power over the individual choices of every man, woman and child.

For the first time in the history of the Republic, federal law requires virtually every American citizen to purchase a product. Those who do not must pay money to the federal government.

Today, the mandatory product is health insurance. Tomorrow, look for purchase mandates for electronic cars, solar panels, soybean burgers, vegetables or whatever the nanny state wants you to do.

When the law forces law-abiding citizens to pay money to the government, we call the payment a tax. When citizens must pay money for violating the law, we call it a penalty or a fine.

Obamacare mandates a payment to the government by those who violate the requirement to buy health insurance. Is that a tax or a penalty?

“I can make a firm pledge,” Obama repeatedly and emphatically promised, “no family making less than $250,000 a year will see any form of tax increase.” Obama said his no-new-taxes guarantee encompassed all forms of taxation: “Not your income tax, not your payroll tax, not your capital gains taxes, not any of your taxes.”

When the Obamacare bill gained momentum in Congress, observers noted that the law imposed a massive tax increase on the very people Obama promised not to tax.

Responding to this charge, Obama said that the mandatory payment is “absolutely not a tax increase.” He and the other proponents of the legislation, which squeaked through the House of Representatives by a margin of just seven votes, sold the law to the American people saying that it was not a tax.

Then, as I wrote in April, the Obama administration shamelessly argued that the Supreme Court needed to uphold Obamacare because it was a tax.

Got that? When you’re selling the law to the American people, it’s “absolutely” not a tax. When you’re selling the law to five unelected, life-tenured lawyers in robes — it’s most emphatically a tax. The people can have their tax and eat it too.

Court-watchers all thought the tax argument was a long shot.

For one thing, not a single lower court had found that the federal taxing power authorized Congress to impose Obamacare’s mandate for everyone to buy health insurance.

For another thing, federal law requires taxpayers to pay a tax before they can legally challenge it in court, and Obamacare’s purchase mandate does not kick in for another two years.

Plus, Obama and many others in the administration had said ad nauseam that the Obamacare payment is not a tax. You would think that federal officials who are taking money out of people’s pockets should own up to what they are doing.

No such luck. The administration and its lawyers had been reading their Emerson: “Speak what you think now in hard words, and tomorrow speak what tomorrow thinks in hard words again, though it contradict everything you said today.”

That’s nice personal advice from a pep talk about self-reliance. But it leaves something to be desired when applied to a government of laws, and not of men.

It’s one thing for a politician to take logically incoherent positions. It’s quite another for the Supreme Court to do so. Least of all did anyone expect that from Chief Justice Roberts.

One of the chief justice’s law professor defenders called his reasoning “legally incoherent all over the place but strategically brilliant.” Last I checked, we don’t ask our judges to be strategic thinkers. Legal coherence would be just fine, thank you.

Roberts flatly rejected the administration’s arguments that the federal commerce power authorized Congress to enact Obamacare. His passionate defense of limited government and federalism would have made James Madison and Alexander Hamilton proud. Roberts spoke gravely of “the country the Framers of our Constitution envisioned.”

After this solemn description of the Framers’ vision for our country, Roberts turned tail and ran directly in the opposite direction. Conceding that “the statute reads more naturally as a command to buy insurance than as a tax,” he proceeded to conclude that Obamacare’s purchase mandate is indeed a tax and therefore hunky dory.

“Because the Constitution permits such a tax,” Roberts said, “it is not our role to forbid it, or to pass upon its wisdom or fairness.” In other words: don’t blame me, blame any seven congressmen who could have voted against Obamacare but didn’t.

That’s just the beginning of the incoherence. Remember that federal law prevents any court — even the Supreme Court — from hearing a tax challenge until after a person pays the tax. Yet the individual mandate does not take effect until 2014.

So how could the mandate survive as a tax? If the mandate is a tax then the Supreme Court did not even have authority to hear the case.

Roberts decided that the mandate is not — repeat not — a tax under the statute that says people cannot challenge a federal tax law until they have already paid the tax. He concluded that Obamacare does not impose a tax because the statute does not call the mandate a tax.

“Congress,” Roberts said, “chose to describe the ‘shared responsibility payment’ (or individual mandate) imposed on those who forgo health insurance not as a ‘tax,’ but as a ‘penalty.’”

Wait a second. To uphold the mandate as a valid exercise of the taxing power, Roberts had to determine that the payment actually is a tax.

As far as Roberts is concerned, the individual mandate can be whatever it needs to be. When the mandate needs to be a “penalty” to fall outside of the statute that prohibited the Court from hearing a tax case, then it’s not a tax. When the mandate needs to be a “tax” to fall within the federal taxing power, well of course it’s a tax.

The four conservatives denounced Roberts’s magic trick. “That carries verbal wizardry too far,” they said, “deep into the forbidden land of the sophists.”

In April, I described how Justice Harlan Stone — through an inappropriate advisory opinion — gave Franklin Roosevelt’s labor secretary, Frances Perkins, the winning design for structuring Social Security so that the Supreme Court would uphold it.

“You can do anything under the taxing power,” Stone whispered to Perkins at a cocktail party. And yet, as broad as Stone’s claim may sound, it was too modest.

As it turns out, Congress can now do anything, period. It can take over a sixth of the national economy and require all citizens to purchase health insurance.

It doesn’t matter if the president insists that the legislation is not a tax. It doesn’t matter if the statutory text says it’s not a tax.

Even if Congress doesn’t use the taxing power, the Supreme Court will.

Gayle Trotter is a writer, lawyer, and mother of six who lives in Washington, D.C. Follow her on Twitter.