If the massive gender-discrimination lawsuit known as Dukes v. Wal-Mart goes to trial someday, the plaintiffs won’t be able to rely on a legal memo in which Wal-Mart’s former lawyers at Akin Gump Strauss Hauer & Feld warned the retailer that it had a gender-discrimination problem.

A judge in San Francisco concluded Tuesday that the 1995 memo is shielded by attorney-client privilege, even though a whistleblower leaked it to The New York Times in 2010. U.S. Magistrate Judge Jacqueline Scott Corley ruled that the leak was "unauthorized and involuntary," and that Wal-Mart lawyers took sufficient precautions to keep it confidential.