ShotgunGuide- Official Rules for Calling Shotgun:

“Section III – The Survival Of The Fittest Rules (a.k.a The Bastard Rules)

1) If the driver so wishes, he/she may institute the Survival Of The Fittest Rules on the process of calling Shotgun. In this case all rules, excepting 1.8, are suspended and the passenger seat is occupied by whoever can take it by force.

2) The driver must announce the institution of the Survival Of The Fittest Rules with reasonable warning to all passengers. This clause reduces the amount of blood lost by passengers and the damage done to the vehicle.

3) Please follow the above rules to the best of your ability. If there are any arguments or exceptions not covered in these rules, please refer to rule 1.8.”