Penalty after whistle

[RefWEB]

1. Penalties can (and most argue should) be called after whistles to discourage the post whistle garbage. At the amateur level, referees are encouraged to keep the post whistle stuff to a minimum.

2. Officials should call the infraction what it is. Nowhere in the book does it say you can only crosscheck or trip while play is on. If I crosscheck a guy in the back after a whistle, I should expect to get a crosschecking penalty.