put a note on his bike not to park there, give it 1 day to change... if he still doesn't listen ? call parking enforcement to get him a ticket ...
there is no reason a rider should be parked in a handicap spot unless he's got a handicap permit. park anywhere else, on the curb, by the building if you want to be next to the door, but in the handicap ? ...
i have 0 patience for these people since I used to have a grandfather who was in a wheelchair. He had these stupid-arse people doing this to him all the time...