Washington was the first to put forth some variation on Executive Privilege, re Congress' request for some information or the other on a treaty (I think the Jay Treaty, but I could be wrong).  The Rules of Evidence didn't come along until the late 60s, IIRC.

Rather, my meaning was that the Executive privilege applies like every other evidentiary privilege, and those are applied through the 500 series in the Rules of Evidence.  I.e., the party seeking the protection of the privilege must raise it, then the court decides whether it applies and, if so, how far.

What Cheney v. US District Court said was, that the Preznit does not, in the first instance and in the context of a civil suit's discovery phase, have to lead off in the District Court by invoking the executive privilege (which may have constitutional roots - but who cares whence it came, as all privileges save the Fifth Amendment are "derived from use and experience" or some similar language in the Rules).  Rather, the Executive branch may seek to limit discovery in the civil suit by "other means".  [In Cheney, Deadeye was considered an adviser to part of the Executive Branch because the Preznit had created this committee comprised of Executive branch officials and asked Deadeye to head it and give him advice.  That energy company executives joined in, no one wanted to touch.] The "other means" would include seeking mandamus in the Court of Appeals to redo or overturn a discovery order issued by the District Court.  The use of mandamus circumvents the ordinary rule barring interlocutory appeals (which one over a discovery dispute clearly would be).