Also, the ruling given here seems wrong: http://forums.pineboxentertainment.com/t/multi-player-q1-definition-of-your-when-collaborating/1767
If you don't control the posse (i.e. if you are sending dudes to join another player's posse), you should not be able to play effects that refer to "your posse".
David, does your ruling in the previous thread suggest a change to AEG's multiplayer rules? It seems under AEG's rules, it is pretty clear that a third-party player would not be allowed to play Outgunned in a shootout as a third party participant (to use the example given in the last thread).
This is the part of AEG's rules that I am asking if you are changing. Your ruling goes completely counter to the AEG multiplayer rules:
Effects that refer to "your posse" can only be played by either the leader or the mark i.e. the players who have a posse. Third party players do not have a posse and so cannot play such cards.