It is a well-known maxim that the attorney-client privilege "extends only to communications and not to facts." Upjohn Co. v. United States, 449 U.S. 383, 395 (1981). It is similarly well established that while the identity of a client typically is not protected from disclosure, the privilege can be invoked to bar revealing a client's identity when doing so will necessarily disclose the substance of a privileged communication. See United States v. Liebman, 742 F.2d 807, 809 (3d Cir. 1984). These principles frame the conundrum presented when the Government seeks to compel lawyers to disclose their clients' identities.