THREE years ago Chief Justice John Roberts infuriated conservatives when he cast a deciding vote to uphold the Affordable Care Act, also known as Obamacare. On March 4th, when the justices heard arguments in King v Burwell, the latest episode in what Justice Elena Kagan called a “never-ending saga” of challenges to the law, the chief kept his poker face. He was all but mum for the 80-minute hearing.

The issue in King is whether five words in a 1,000-page, ill-drafted and almost incomprehensible statute spell doom for the rest of it. Obamacare provides subsidies to the cash-strapped when they buy health insurance through “exchanges established by the state”. But 34 states opted not to set up exchanges. The federal government set exchanges up for people in those states, and offered them subsidies like everyone else. Since the law does not expressly allow subsidies for people who buy insurance on a federal exchange, the challengers say, such payments are illegal.

Michael Carvin, the challengers’ lawyer, called the case “straightforward”. Stephen Breyer, a liberal justice, disagreed. “What’s the problem,” he asked, with viewing a federal exchange as the functional equivalent of state-run markets? Donald Verrilli, the solicitor-general, who made a bumbling defence of Obamacare in 2012, took off his gloves this time. The challengers’ view “makes a mockery” of the law and leads to a “textual brick wall”, he said, “revok[ing] the promise of affordable care”. Here Justice Antonin Scalia huffed that while “it may not be the statute they intended”, it is “the statute that they wrote”. Only Congress, not the justices, he said, has the authority to “rewrite” a bad law.

The stakes are high. With subsidies removed, many people would find their insurance policies unaffordable. The Urban Institute estimates that 8.2m Americans would lose coverage if the challengers prevail. And the broader insurance market would be thrown into turmoil unless Congress acted swiftly to re-draft the law. Given the vast differences between the Republican-controlled Congress and the president, a deal to revise Obamacare would be nearly impossible to reach.

On the court, there seem to be three votes to gut Obamacare and four to salvage it. As for the other two, Mr Roberts was inscrutable and Justice Anthony Kennedy may have revealed his hand when he said that coercing states to set up their own exchanges raised a “serious constitutional question” of federalism. A ruling is expected by the end of June.