Question

whta makes sure that everyone followa the rules in a game of football

Answer 1

There are game officials who can impose penalties or other corrections for violations during the game. There are the players themselves and their coaches. In some cases there may be rules the league or other circuit imposes that are administered by league officials that can have effects beyond the game during which the violation occurs. But ultimately, nobody can make sure that everyone follows the rules; there are bound to be violations at times. The ultimate sanction against severe and persistent departure from the rules is that nobody plays with you if you're known to play like that.