The Microsoft case is about extraterritorial limits of search warrants, not subpoenas. US corporations can be compelled by subpoena to appear before court and

The Microsoft case is about extraterritorial limits of search warrants, not subpoenas. US corporations can be compelled by subpoena to appear before court and turn over documents/evidence they control regardless of what country they are stored in. No idea about administrative subpoenas which I believe include National Security Letters though. I imagine it is the same as the judicial subpoenas.