Ilya Somin explains why:
In its recent controversial decision in Halbig v. Burwell, the US Court of appeals for the DC Circuit ruled that people purchasing health insurance under the Affordable Care Act are only eligible for federal tax credits if they do so through an exchange established by a state. Although the plain text of the ACA indicates that tax credits are only available to those who purchase insurance in an “[e]xchange established by the State,” many critics claim that the court should have refused to enforce this language because it creates an “absurd” result because it undermines the ACA’s goal of expanding access to health insurance.
There is indeed Supreme Court precedent stating that courts can sometimes refuse to enforce the plain meaning of a statute where doing so creates an absurd result. But, as Judge Griffith’s D.C. Circuit opinion emphasizes (quoting an earlier DC Circuit ruling), it is limited to cases where enforcement of the text would “render[ the] statute nonsensical or superfluous or . . . create an outcome so contrary to perceived social values that Congress could not have intended it.” In this case, however, the result is far from nonsensical. Indeed, the DC Circuit’s interpretation of the ACA reflects the sort of “cooperative federalism” approach that left of center academics and policy experts often praise in other contexts.
Read the whole thing, which is quite informative. Read as well Ed Whelan’s reply to Rick Hasen.