Just move his shit when he leaves for lunch or at the end of the day. If he moves it back make his life hell by bumping him like he does you. If he complains tell your supervisor and his that had he put his stuff in the appropriate positions this bumping would not have occurred.
On a side note this person sounds like the quiet power type of person. In his idiotic mind he feels he has some power over you because he will not move his stuff and he annoys you with those bumps just to remind you of his power.
On a side note this person sounds like the quiet power type of person. In his idiotic mind he feels he has some power over you because he will not move his stuff and he annoys you with those bumps just to remind you of his power.