On November 30, 2009, the California Supreme Court issued its ruling in the matter of Costco Wholesale Corporation v. Superior Court (Randall), S163335, upholding the protection afforded confidential attorney-client communications and affirming the sanctity of the attorney-client relationship. The decision vacated a trial court ruling which ordered that a redacted attorney opinion letter to the client be produced to opposing counsel.

In June 2000, Costco Wholesale Corporation ("Costco") retained counsel to provide legal advice on whether warehouse managers were exempt from California's wage and overtime laws. Costco's counsel produced a 22-page opinion letter based in part on facts from interviews with two warehouse managers. Costco, counsel and the managers all understood and agreed that the communications and opinion letter would remain confidential.

Several years later, a class action lawsuit was filed against Costco alleging that some warehouse managers were misclassified as "exempt" employees from 1999 to 2001 resulting in Costco's failure to pay overtime wages. During the discovery process, the plaintiffs sought to compel the opinion letter. Costco objected arguing attorney-client privilege and attorney work product doctrine.