I love to be clear, and there was an IM about the reroll rule. I don't like cheesing up a fun rule like this.
If you're wearing your Pathfinder Society faction T-shirt while playing an official Pathfinder Society Scenario, you're allowed to reroll one die roll per scenario! (You must announce that you are using your reroll before the GM has announced the result of your previous roll.)
Let me use my Floor Judge-like powers(tm)...
1) This is ONLY for Pathfinder Society games.
2) One d20 reroll roll per four hour session.
3) On "announcing the result", looking at a 9 to hit, and knowing that is a miss is different than the Judge saying you fail.
Judges should be forgiving with the rule about "verbalizing the result", and let that slide most times. Under no circumstances shall a player wait to find out if they missed, before announcing a reroll.
4) You CANNOT re-roll a GM's roll.
5) You CANNOT re-roll someone else's roll.
6) You CANNOT re-roll damage rolls.
7) You have to wear the shirt. You have to have it on at the beginning of the session and through the session. The reroll is for the shirt wearing person only and it has to match the faction you are playing.
8,9,10) Do not taunt the shirt. Do not make faces at the shirt. The shirt does not care, yet, the shirt will grant a reroll.
11) Tacos rule. That is official.