Here is the section of the 2000 Code of Laws that deals with this issue. As umpires, we are limited in what we can do, however Law 42.3 states quite clearly the protocol that needs to be followed in cases of ball tampering.
The match ball – changing its condition
(a) Any fielder may
(i) polish the ball provided that no artificial substance is used and that such polishing wastes no time.
(ii) remove mud from the ball under the supervision of the umpire.
(iii) dry a wet ball on a towel.
(b) It is unfair for anyone to rub the ball on the ground for any reason, interfere with any of the seams or the surface of the ball, use any implement, or take any other action whatsoever which is likely to alter the condition of the ball, except as permitted in (a) above.
(c) The umpires shall make frequent and irregular inspections of the ball.
(d) In the event of any fielder changing the condition of the ball unfairly, as set out in (b) above, the umpires after consultation shall
(i) change the ball forthwith. It shall be for the umpires to decide on the replacement ball, which shall, in their opinion, have had wear comparable with that which the previous ball had received immediately prior to the contravention.
(ii) inform the batsmen that the ball has been changed.
(iii) award 5 penalty runs to the batting side.
(iv) inform the captain of the fielding side that the reason for the action was the unfair interference with the ball.
(v) inform the captain of the batting side as soon as practicable of what has occurred.
(vi) report the occurrence as soon as possible to the Executive of the fielding side and any Governing Body responsible for the match, who shall take such action as is considered appropriate against the captain and team concerned.
(e) If there is any further instance of unfairly changing the condition of the ball in that innings, the umpires after consultation shall
(i) repeat the procedure in (d)(i), (ii) and (iii) above.
(ii) inform the captain of the fielding side of the reason for the action taken and direct him to take off forthwith the bowler who delivered the immediately preceding ball. The bowler thus taken off shall not be allowed to bowl again in that innings.
(iii) inform the captain of the batting side as soon as practicable of what has occurred.
(iv) report this further occurrence as soon as possible to the Executive of the fielding side and any Governing Body responsible for the match, who shall take such action as is considered appropriate against the captain and team concerned.
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The crux of the law is that as long as no artifical substance is used to damage the ball and in the Umpire's opinion, the players aren't damaging the ball, then it's ok. The Umpires must make regular inspections of the ball at all intervals and at the fall of wickets or at the end of each over to ensure that there is no tampering. If they feel that there is through these inspections and watching bowlers and/or fielders during play, then these protocols apply.
Hope this clears it up guys...
Eyes