Q: A competitor hit a ball into a clubhouse which was not out of bounds and had not been declared an integral part of the course. In order to play it out, he opened a window, claiming that it was a movable (or partially movable) obstruction. Was this permissible?
A: Yes. The clubhouse was an immovable obstruction. However, any part of it designed to be movable, such as a window or door, may be moved to any position if this can be done without undue delay. The same principle would apply if the clubhouse had been declared an integral part of the course.
The Armchair Golfer
(Source: USGA)