The Costco case took a circuitous route through the courts. The appellate court summarily denied the writ of mandate. The California Supreme Court reversed and instructed the appellate court to look at the issue substantively. The appellate court reviewed the issue and then denied the writ, finding that Costco couldn't make the required showing of "irreparable harm" if it was ordered to turn over the redacted document. A second appeal to the California Supreme Court finally yielded Costco, and defense counsel everywhere, the relief they sought. The court ruled that the order for Costco to disclose even part of the memo was an error.
"The attorney-client privilege attaches to a confidential communication between the attorney and the client, and bars discovery of the communication irrespective of whether it includes unprivileged material," Judge Kathryn Werdegar wrote for the unanimous court. "It is the actual fact of the transmission [of documents,] which merits protection, since discovery of the transmission of specific public documents might very well reveal the transmitter's intended strategy."