Roberts, a conservative appointed by former President George W. Bush, argued that it was. His 22-page majority opinion said the court's job is to apply congressional intent when it was clear, and to figure out from the entire law what a specific disputed piece of language means if the provision's intent is vague.
The six justices concluded that the language was ambiguous, and that the "established by the state" clause was one of a long list of drafting mistakes stemming from the fierce battle in Congress before it was passed. If the language is ambiguous, mainstream statutory construction requires courts to figure out which interpretation better fits the overall goal of what Congress set out to do.
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"If the statutory language is plain, we must enforce it according to its terms," Roberts wrote. "But oftentimes the meaning—or ambiguity—of certain words or phrases may only become evident when placed in context. So when deciding whether the language is plain, we must read the words in their context and with a view to their place in the overall statutory scheme. Our duty, after all, is 'to construe statutes, not isolated provisions.'"
From there, Roberts cited the experience of states like Washington that set up health insurance reforms without subsidies, only to see their health insurance markets unravel as rates skyrocketed and people refused to buy coverage. Since Obamacare would also collapse without the subsidies, forcing premiums to skyrocket in the 34 states that left the job of selling insurance to their residents to the federal government, Roberts said Congress couldn't have meant to deny subsidies to residents of those states.
"The tax credits are among the Act's key reforms, involving billions of dollars in spending each year and affecting the price of health insurance for millions of people," Roberts wrote. "Whether those credits are available on Federal Exchanges is thus a question of deep 'economic and political significance' that is central to this statutory scheme."