Rule #?: When a player wins an event, they must take the event coin/prize given, if any. After multiple transgressions, the individual (or gang if applicable) will be punished by being warped out of all future events of that host (and potentially future hosts) for the rest of the day. If transgressions continue for a series of days, jailing can occur for "Event Disruption" under the judgement of the administrator.

Everything else is basic common sense:
The event host can choose to alter any normal methods of play (i.e. no shotguns in Tag Team Spar, staff stick chasing in elegant chance).
Cheating is not allowed (i.e. Spear Glitch in Bush Race).
Event coins may not be given after a player wins an event, because certain groups of people can constantly win events and give all of the event coins to one (potentially undeserving) player.

Honestly, there is no need for an official rule book. If you are really into events and want to be the most law-abiding player, learn from your mistakes or mistakes of others. If you are caught breaking an unofficial/unknown rule, you would usually get a warning and the event would be hosted again.