Rule 7: (UK): "Don't take the piss".
"Taking the piss" means being unreasonable, or taking liberties at the expense of others. In American English, it roughly translates to "don't be a dick" or "don't be a jerk".
Rule 7 is widely accepted among UK larps, and is used as a guide to interpreting edge-cases in the rules. It reflects a widespread view that larping is supposed to be fun, it requires collaboration, and aggressive rules interpretation runs counter to that spirit.