The most important sentence in Justice Roberts’s opinion yesterday upholding the Affordable Care Act is the least arresting. The new ObamaCare tax, which Roberts created in order to uphold the Act, “makes going without insurance just another thing the government taxes, like buying gasoline or earn­ing income.”

Despite Roberts’s blithe assurance that a tax on “going without insurance” is nothing new, the fact is that this one sentence expands the powers of the federal government beyond anything previously known. For the first time in U.S. history, the government may tax what you and I do not do. Roberts calls these failures to act “omissions.” For the life of me, I can’t think of an omission — a refusal to act — the government now taxes. Penalties may be imposed for failing to do something (library fines for not returning a book on time, speeding tickets for not observing the speed limit, restaurant fines for not adhering to the health code). But even these require affirmative acts first: I must first check out the book, drive too fast, open a restaurant and scatter food about for the roaches and the rats. But just sitting around and minding my own business? For the first time in U.S. history, I can be taxed for that.

Now, it may be objected that Roberts is entirely correct. This is nothing new. The government has been taxing inactivity and omissions for a long time. On some such understanding, income-tax deductions for you are taxes on me. I rent my house; you own yours. You get the mortgage deduction; I pay a higher tax than you — a renter’s tax, you see, a tax on not owning a home.

But this objection is broken-backed. Here’s why. If you were to start over, designing a tax code from scratch, and if you wanted to begin by imposing a tax on renters, how would you do so? By taxing renters. For the affirmative act of renting a place to live. In the absence of a tax on homeowners, however, this newfangled renter’s tax could hardly be described as a tax on the omission of not owning a home. Next you might impose a tax on cigarettes. But would you call this a tax on not not smoking? Ockham’s razor would slice away the double negative: it’s simply a tax on smoking.

Under the current system, moreover, you can forego the mortgage deduction, placing yourself on the same tax level as us renters. Granted, it’s unlikely that you will ever do so — but (in language that Justice Roberts uses elsewhere in his opinion) it’s “fairly possible.” The mortgage deduction is optional. Not the ObamaCare tax, though. If I don’t pay it (and don’t pay for health insurance either), the IRS can withhold my tax refund. The ObamaCare tax is mandatory. For the first time in U.S. history, the federal government is empowered to impose a mandatory tax on the failure or refusal to act.

Justice Roberts anticipated these criticisms. “Even if only a tax,” he said, the payment due for not buying health insurance “remains a burden that the federal government imposes for an omission, not an act.” He tried to “allay” this “concern” by observing that the ObamaCare tax “nonetheless leaves an individual with a lawful choice to do or not do a certain act, so long as he is willing to pay a tax levied on that choice.”

But this “choice” is an illusion of choice. When it comes to cigarette taxes or gasoline taxes, I have a real choice — I can choose not to smoke, not to drive. My choice is between activity and inactivity. Omission waives the tax. When it comes to the ObamaCare tax, however, my choice is to pay or pay. Either I pay for health insurance or I pay the tax. My choice is between two variations of the same activity. The government is compelling me to action I might otherwise not have taken.

The familiar example of something the government might compel U.S. taxpayers to purchase is broccoli. Justice Ruth Bader Ginsburg dismisses this example as “the broccoli horrible.” But in his dissent, Justice Anthony Kennedy takes it seriously. What if broccoli were found to contain unique cancer-fighting properties? Your refusal to consume it would then produce “health-care costs that are a burden on the rest of us,” Kennedy said, in which case — on the logic of the ObamaCare tax — “moving against those inactivities will also come within the federal government’s unenumerated problem-solving powers.”

Anyone who believes this is an abstract phobia has not been paying attention to the culture during the past two decades. All sorts of omissions have come under attack in recent years — pharmacists who refuse to dispense abortifacients, churches and yeshivot that refuse to ordain women, institutions and jurisdictions that refuse to recognize same-sex marriages, golf clubs that refuse to admit women. Statistical disparities are advanced as prima facie evidence of omission — higher average salaries for men than women (or higher average salaries for whites than blacks), magazines that publish fewer women than men (or fewer blacks than whites), schools with lower admission rates for blacks than whites (they rarely have too few women). The new taxing authority created out of whole cloth by Justice Roberts is a powerful tool for compelling compliance with the cultural fashion of the moment. Augusta National can now be taxed for refusing to admit women, and wedding photographers can now be taxed for refusing to snap pictures at same-sex nuptials.

By creating the ObamaCare tax, the Supreme Court of the United States has created a means for the federal government to slap a price on non-conformity.