NANCY PELOSI, a former Democratic Speaker of the House, once said that “we have to pass [Obamacare] so that you can find out what is in it.” It turns out she was wrong. The Affordable Care Act was passed in 2010. But four in ten Americans still say they don’t understand how it will affect them. And judges can’t figure out what it means, either.

On July 22nd two appeals courts offered utterly contradictory interpretations. In Halbig v Burwell, a three-judge panel in Washington, DC ruled that Obamacare does not empower the government to offer subsidies to Americans who buy health insurance through federal exchanges. A couple of hours later in King v Burwell, a panel in Virginia took the opposite view.

For now, Barack Obama’s lawyers say that nothing will change. But how this mess is sorted out will matter a lot. Republicans have attacked Obamacare for years, to little avail. But if Halbig stands, it could be the tugged thread that causes the whole reform to unravel.

Obamacare requires all Americans to have health insurance or pay a fine, and obliges insurers to charge the sick and the healthy the same premium. It urges states to create exchanges where individuals can shop for insurance. To make that insurance affordable, it offers subsidies to individuals earning between $11,670 and $46,680 a year. (Many of those who make less than that will qualify for Medicaid, a public health programme for the poor.)

Amazingly, it took nearly 1,000 pages of gobbledygook to turn this framework into the law of the land—excluding the much larger volume of supplementary regulations. Since the federal government could not force states to set up health-insurance exchanges, Obamacare created a fallback. In states that did not create an exchange, the federal government could do so on its behalf. To Democrats’ surprise, 36 states left the job to Uncle Sam.

Unfortunately Obamacare’s text stipulates that subsidies are available through exchanges “established by the State”. It does not mention subsidies for people who enrolled via federal exchanges. In 2012 the Internal Revenue Service (IRS) said it was fine to interpret the law as providing subsidies on both state and federal exchanges. The plaintiffs in Halbig and King, along with those in two other pending cases, argued that since the law did not explicitly allow subsidies on federal exchanges, they are illegal.

Mr Obama’s lawyers insist that Congress intended to make Obamacare subsidies broadly available. Two out of three judges in Halbig had no time for this argument. They declared that “a federal exchange is not an ‘exchange established by the State’” and the law “does not authorise the IRS to provide tax credits for insurance purchased on federal exchanges.” Earlier, in oral arguments, Judge A. Raymond Randolph had quipped, “If the legislation is just stupid, I don’t see that it’s up to the court to save it.” The judges in Virginia, by contrast, sided with the IRS, explaining: “we uphold the rule as a permissible exercise of the agency’s discretion.”

The resulting confusion should leave Republicans elated. They have new reason to hope that Obamacare will collapse. And they have new support for their claim that Mr Obama is a feckless autocrat who ignores the law. But the rulings have implications far beyond the political.

If Halbig stands—something that may remain uncertain until the matter reaches the Supreme Court—the IRS will be unable to fork out insurance subsidies in the 36 states with federal exchanges. That would jeopardise Obamacare’s mandate that employers above a certain size offer health insurance for their staff—the penalties that back up this rule kick in when a worker receives a subsidy on a public exchange.

More importantly, Halbig would scrap subsidies for nearly 5m people who received them this year. If those people remain in the same health plans, the amount they would have to pay out of their own pocket for insurance would jump by an average of 76%. However, many would be able to claim that they could not afford this, so they would become exempt from the individual mandate. That would, in turn, undermine the broader individual market. If too few healthy people bought coverage, prices would rise, making them even less likely to buy insurance in the future. Obamacare has faced many frivolous threats. This one could be existential.