18-3. By Opponent, Caddie or Equipment in Match Play
a. During Search
If, during search for a player’s ball, an opponent, his caddie or his equipment, moves the ball, touches it or causes it to move, there is no penalty. If the ball is moved, it must be replaced.
b. Other Than During Search
If, other than during search for a player’s ball, an opponent, his caddie or his equipment, moves the ball, touches it purposely or causes it to move, except as otherwise provided in the Rules, the opponent incurs a penalty of one stroke. If the ball is moved, it must be replaced.