I have noticed some curiosities in concurring and dissenting opinions in Supreme Court cases this term, and will remark on a few.

In Decker v. Northwest Environmental Defense Center, the Supreme Court upheld an interpretation by the Environmental Protection Agency of one of the agency’s own regulations, saying that “deference is accorded” to any agency’s interpretation of its regulations. Justice Antonin Scalia dissented, saying that to defer to an agency’s interpretation of its own regulations “violate[s] a fundamental principle of separation of powers—that the power to write a law and the power to interpret it cannot rest in the same hands.” Scalia’s concern is that the agency will issue a vague regulation, intending to alter it by interpretation, thereby avoiding the required procedures (such as notice of a proposed regulation, and an opportunity for people who may be affected by it to comment).

That is a valid concern, but it doesn’t justify a blanket refusal to grant some deference, some leeway, to agency interpretations of their own regulations. The regulation may deal with a highly technical matter that the agency understands better than a court would; its interpretation may be in the nature of explanation and clarification rather than alteration. Scalia proposes that in all cases in which an agency’s interpretation of its own regulation is challenged, the reviewing court should resolve the challenge “by using the familiar tools of textual interpretation.” Those tools are notably unreliable, especially when dealing with a technical regulation. In Decker, the regulation concerned storm water runoff from logging roads.

Read more at Slate