On Monday, the Supreme Court will hear arguments in a little-noticed case that threatens to create a new exception to the attorney-client privilege. Worse, no justification for a new exception for "insignificant" legal-advice communications has been briefed or offered. Over 40 years ago, in Upjohn v. United States (1981), government lawyers urged the court to choose among different privilege "tests." Chief Justice William Rehnquist, writing for a unanimous court, rejected the request. "[W]e … sit to decide concrete cases, and not abstract propositions of law. We decline to lay down a broad rule or series of rules to govern all conceivable future questions in this area." The current court should heed this wise counsel when on Monday it considers whether to leave some lawful client-lawyer conversations unprotected.