The phrase "to blow the whistle" means to reveal or report something wrong or illegal that is happening, especially within an organization. Full definition
Anyone who does not blow the whistle if they discover potential corruption could be charged with a misdemeanor. (wamc.org)
You would think a former professional footballer would recall that a match isn't over until the referee blows his whistle after 90 minutes plus injury time wouldn't you? (justarsenal.com)
The players swim up and down, and the ref blows his whistle for no apparent reason and the ball goes over to the other team. (sportstarsmag.com)