Out Of Bounds Post
Question: - Am I allowed to move a white stake, marking out of bounds, in order to play my shot?
Answer: - No. You are not allowed to move an out of bounds post.
The out of bounds is determined by the inside points, at ground level, of the stake.
The stake is therefore out of bounds so it can not be removed. (See R&A Rules Definition of Out of Bounds).
You are, however, allowed to move stakes defining a Water Hazard as these are Obstructions. (See R&A Rules Definition Water Hazard)
Relief from yellow or red stakes in covered under Rule 24-1a. If the ball does not lie in or on the Obstruction, the Obstruction may be removed.