So, Lambert says, the ACA’s penalties are too low to prod the healthy to purchase insurance, even given ACA’s subsidies for purchasers. The ACA’s authors probably understood this perverse incentive and assumed that once Congress passed the ACA with penalties low enough to be politically palatable, Congress could increase them.

But Roberts’s decision limits Congress’s latitude by holding that the small size of the penalty is part of the reason it is, for constitutional purposes, a tax. It is not a “financial punishment” because it is not so steep that it effectively prohibits the choice of paying it. And, Roberts noted, “by statute, it can never be more.”As Lambert says, the penalty for refusing to purchase insurance counts as a tax only if it remains so small as to be largely ineffective.

Unable to increase penalties substantially, Congress, in the context of “guaranteed issue” and “community rating,” has only one way to induce healthy people to purchase insurance. This is by the hugely expensive process of increasing premium subsidies enough to make negligible the difference between the cost of insurance to purchasers and the penalty for not purchasing. Republicans will ferociously resist exacerbating the nation’s financial crisis in order to rescue the ACA.