A set of rules that must be followed when you are wearing a Harry Potter shirt and one of your classmates/friends/family members are wearing a Twilight shirt.
1. You cannot talk to this person.
2. You cannot tell them about the rules, they either know or they don't. If you tell them about the rules, there will be a penalty.
3. You may talk to them if and only if you are telling them that you cannot talk to them, or telling them that it is against the rules.
4. The rules must be followed, it doesn't matter if it's your mom, dad, best friend, dog, it doesn't matter.
5. If they start making fun of your shirt, you may talk to them just to tell them off or argue.
6. You must defend your shirt.
7. If necessary, you may spill something/spit on their shirt.
Today on the bus, Bob was wearing a Team Jacob shirt, I was wearing a Gryffindor shirt. I had to follow the Harry Potter vs. Twilight rules for the rest of the day.