From the Group Policy - See the 'Policy' link at top of the page

Inside Conflict Zones the following rules apply:
It is not allowed to attack a neutral player (a player not having chosen a faction)
It is not allowed to attack another player while being neutral (not having chosen a faction oneself)
It is not allowed to attack another player on the own chosen faction
Only if both players have actively chosen opposing factions may they engage in combat
It is not allowed to exit and enter a warzone in rapid succession for the sole purpose of targeting other players. Only if the wrong faction was chosen by mistake or by mutual agreement of the present players (For example in order for everybody to join the same faction).
As for me - I always play it safe and do CZ's in Solo
