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The most honest answer is probably some version of, who knows? It's a messy statute; this part was written in a hurry—maybe it's just a mistake.
But the Justice Department can't really make that argument before the Court, legal experts said, because courts try to avoid reading parts of any legislation as extraneous. If Congress said something, the courts tend to assume that it did so for a reason.
"It's a simple argument for the petitioners," said Chris Walker, a law professor at Ohio State University and a former clerk to Justice Anthony Kennedy.
So, the government's best bet is to argue that "established by the State" belongs there, but doesn't mean what it sounds like. The Justice Department says "established by the State" refers to any exchange, no matter who established it.
The statute treats state- and federally run exchanges as equivalent in other ways and, the government argues, the statute as a whole indicates that Congress intended for the federally run exchanges to "stand in the shoes" of the states.
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"That phrase is a term of art that includes both an Exchange a State establishes for itself and an Exchange HHS establishes for the State," the Justice Department said in a brief to the high court.
Still, everyone who supports Obamacare and wants to see this case fail would be happier if the words "established by the State" weren't there. And that makes them a problem. The question is, how big a problem?
Under the Justice Department's interpretation, critics argue, "established by the State" is a "term of art" that doesn't mean anything—the sentence would mean the same thing with those words as it would without them. So, again, why are they there?
"Why would Congress add unnecessary words that, on any reading, say precisely the opposite of what it supposedly meant?" the challengers' brief asks.
Legal experts said David Rivkin, who is arguing the case for the challengers, will likely do his best to bring the justices—particularly Kennedy and Chief Justice John Roberts—back to that question.
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The Justice Department has a thorough argument about the most natural way to read other parts of the statute, but when the questioning is confined to "established by the State," it will likely stay pretty circular. The further the justices are willing to branch out, the greater chance the government has of winning.
Realistically, the Justice Department has more ways to win than the challengers. But the silver lining for the law's critics is that their strongest argument is the starting point for the court's analysis.
"The four words are definitely on their side, and then they just have to be able to really hammer home that you can read the rest of the statute consistently with that," Walker said.