I think i understand...


In the anime the first gym battle (Brock vs Ash) the leader asks him if it was his first battle. He also decreed how many pokemon were to be used.

It should also be noted that in every gym to date has a clear area outlined for both trainers and pokemon. Charzard once bailed on Ash by flying outside that area and taking a nap and was disqualified. It is unclear if he was disqualified for leaving the area on purpose, for obviously not participating or being outside the area.


I figure then the gym rules are simple and the following;
Asking for previous experience (etiquette, optional)
Declaring number of pokemon to be used ahead of time
Trainers and pokemon staying inside their designated area when possible (for safety)
No coup de grace (the show never had killing as expected but this might need to be considered that it can happen in your game/world)