American Football IFAF Approved Ruling 9-2-3:I

I. After the ball is ready for play and the umpire (or centre judge) is in his regular position, Team A quickly replaces some players with substitutes, gets set for the required one second and snaps the ball. The umpire (or centre judge) is attempting to get to the ball to allow the defense to match up, but he is unable to prevent the snap. RULING: The play is shut down, the game clock is stopped and the defense is allowed to substitute in response to Team A’s late substitutions. No foul. The play clock is set to 25 seconds and starts on the ready-for-play signal. The game clock starts on the ready-for-play signal or the snap, depending on its condition when play was stopped. The referee informs the Team A head coach that any subsequent such actions will result in a foul against the team for unsportsmanlike conduct (Rule 3-5-2). [Cited by 9-2-3-c]