The DOD is part of the executive branch. The subpoena was issued to someone from the DOD, thus the "executive". The DOD also used "executive privilege" in their bitch letter.

DOJ is part of the executive branch. Subpoenas were issued to them to get unredacted grand jury testimony from the Mueler report as part of the impeachment inquiry. The executive made the same sort of arguments and they've lost the case on multiple points. Course it's not going to be completely resolved until some time next year but it will most likely come down to the main point of whether or not the private information can be made available and nothing to do with whether the subpoena or request is legal or not.

Says the person who will not admit he was wrong about there being no subpoenas issued at all or that there is a high degree of at least circumstantial proof that the the Rudy/Pompeo subpoenas exist given they've said they do. That's some awesome high level reasoning and logic coming from you.