The Official Rules of Golf appear on the About.com Golf site courtesy of the USGA, are used with permission, and may not be reprinted without the permission of the USGA.

22-1. Ball Assisting Play
Except when a ball is in motion, if a player considers that a ball might assist any other player, he may:

(a) lift the ball if it is his ball, or
(b) have any other ball lifted.

A ball lifted under this Rule must be replaced (see Rule 20-3). The ball must not be cleaned unless it lies on the putting green (see Rule 21). In stroke play, a player required to lift his ball may play first rather than lift the ball.

In stroke play, if the Committee determines that competitors have agreed not to lift a ball that might assist any other player, they are disqualified.

22-2. Ball Interfering with Play
Except when a ball is in motion, if a player considers that the ball of another player might interfere with his play, he may have it lifted.

A ball lifted under this Rule must be replaced (see Rule 20-3). The ball must not be cleaned unless it lies on the putting green (see Rule 21).

In stroke play, a player required to lift his ball may play first rather than lift the ball.

Note: Except on the putting green, a player may not lift his ball solely because he considers that it might interfere with the play of another player. If a player lifts his ball without being asked to do so, he incurs a penalty of one stroke for a breach of Rule 18-2a, but there is no additional penalty under Rule 22.

PENALTY FOR BREACH OF RULE:
Match play — Loss of hole; Stroke play — Two strokes.

©USGA, used with permission