Question: can umpire revoke no ball?
Answer: An umpire shall revoke the call of No ball if Dead ball is called under any of Laws 20.4. ... 2.9 (Umpire calling and signalling Dead ball). This is the only law which is related to the revoking of a no ball. The umpires were at fault in yesterday's game since the first umpire did not notice the square leg umpire.