Chief Justice John Roberts was as taciturn at Wednesday's oral arguments as he's ever been since taking the center seat on the bench. He sat passively for most of the questioning and made only one inquiry of real substance, near the end of Solicitor General Donald Verrilli's presentation.

"If you're right — if you're right about Chevron, that would indicate that a subsequent administration could change that interpretation?" Roberts asked.

Sounds like code. Could be very important.

Roberts was referring the "Chevron deference," a doctrine mostly unknown beyond the halls of the Capitol and the Supreme Court. It refers to a 1984 decision, Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., and it is one of the most widely cited cases in law.

It says that when a law is ambiguous, judges should defer to the agency designated to implement it so long as the agency's decision is reasonable.

A decision based on Chevron deference could say to Congress: Fix the law to make it unambiguous. It says to the executive branch: Implementation of the law is up to you.

Verrilli pushed back — gently — on Roberts. He wants the court to find that, read in context, the law is not ambiguous.

Perhaps Roberts was playing devil's advocate, or perhaps his interest in Chevron means something else.

Washington Post