A lot of the points that the New York Times‘ legal correspondent Linda Greenhouse covers today in an overview of the stakes involved in King v. Burwell have been made in various places. But pulled together as they are, you can see exactly how radical an exercise in judicial activism it would take for SCOTUS to agree with the petitioners in this case.

First of all, there’s never been a SCOTUS decision validating anything like the principles of statutory interpretation the anti-ACA camp is demanding:

Statutory interpretation is something the Supreme Court does all the time, week in and week out, term after term. And while the justices have irreconcilable differences over how to interpret the Constitution, they actually all agree on how to interpret statutory text. (They do disagree on such matters as the legitimacy of using legislative history, or on what weight to give a law’s ostensible purpose; I’m referring here to how they actually read a statute’s words.)

Every justice subscribes to the notion that statutory language has to be understood in context. Justice Scalia said it from the bench just last month, during an argument about the proper interpretation of the federal Fair Housing Act. “When we look at a provision of law, we look at the entire provision of law, including later amendments,” Justice Scalia said. “We try to make sense of the law as a whole.”

That militates against the sort of literalist meaning the petitioners are asking for. But worse yet from a conservative point of view, punishing the states for exercising an option ACA clearly provided for–allowing the federal government to create purchasing exchanges for them–would violate supposedly sacred principles of federalism.

A fascinating brief filed in support of the government by an unusual coalition of 23 red-state and blue-state attorneys general (some from states with their own exchanges and others from federal-exchange states) maintains that the challengers’ narrative would “violate basic principles of cooperative federalism by surprising the states with a dramatic hidden consequence of their exchange election.”

This brief, written in the Virginia attorney general’s office, continues: “Every state engaged in extensive deliberations to select the exchange best suited to its needs. None had reason to believe that choosing a federally facilitated exchange would alter so fundamental a feature of the A.C.A. as the availability of tax credits. Nothing in the A.C.A. provided clear notice of that risk, and retroactively imposing such a new condition now would upend the bargain the states thought they had struck.”

There are abundant Supreme Court precedents that require Congress to give states “clear notice” of the consequences of the choices a federal law invites them to make. Justice Samuel A. Alito Jr. invoked that principle in a 2006 case interpreting the Individuals With Disabilities Education Act, a case cited by the 23 attorneys general. The government’s own brief, filed by Solicitor General Donald B. Verrilli Jr., observes that “it would be astonishing if Congress had buried a critically important statewide bar to the subsidies under this landmark legislation” in technical sub-clauses.

Yes, “astonishing” is the right word to describe the implications of a SCOTUS action to blow up the Affordable Care Act. But not necessarily surprising.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.