Although I feel for Ms. Schiavo, I do not remember the President subpoening anyone. That charge could only be laid on the Congress, since Bush has nothing to do with Congressional Subpoenas.
I believe that the Federal Marshalls, controlled by the Executive branch, are responsible for enforcing Congressional supoenas. This whole affair is yet another example of Republican politicians making much sound and fury at the judicial Mullahcracy - signifying nothing. Pure hot air.
The Republican oligarchs have much more important fish to fry - like destroying US sovereignty for their corporate masters. All of the action in the past week was just for show. If the Congress cited Greer for contempt, the Federal Marshals could march in and arrest him at gunpoint, hauling him away in shackles before the TV cameras. It will never happen - the Mullahs are far too useful. They can implement the globalist agenda by judicial fiat and be blamed for the rulings that make people furious, yet remain in place because Congress wouldn't dare to exercise its power to remove them from the bench. A very effective scam.
Legislative issues as in the House, Executive enforces as in US Marshall's