A corporation’s attorney-client privilege may be extended to include a second company and its lawyers, but such a joint privilege covers only those communications that were truly made in furtherance of a shared legal strategy, a federal judge has ruled.

In King Drug v. Cephalon , U.S. District Judge Mitchell S. Goldberg defined the contours and limits of the so-called “community of interest” privilege and ruled that it does not apply where one company took sole control of litigation strategy — even if there was an initial agreement that the litigation would be jointly funded and directed.