I don't think these doors can be closed at all.
You can enable or disable the travel region to the Guild HQ instead (via TriggerActivation()). Additionally you could add an invisible door to block the passage more effectively. DLTCEP offers some functionality in that regard (look for vertices and impeded blocks in the Doors tab).
do you know if it's possible (and if so, using what tools) to edit a map's impassable area on the fly via script?
If not, I will see if I can learn how to use DLTCEP in order to do what you suggested.