This suggestion is purely because I accidentally posted something online and it's all EMC'S fault. Last week I was scrolling through the commands that you could do with a group, and there was one that said you could make it so that group members could hurt each other. Then I posted an pvp event and guess what. only staff can preform this command. How is this EMC's fault. they did not put a proper warning. So, I completely embarrassed myself. EMC needs to add some text after help menu commands to verify if players can preform them. Then this would happen less often.
I'm sorry to hear about what happened. I'm assuming you are talking about toggling it while you are in a group? You would simply type /group PvP to toggle it on/off Be sure to check out this link, as it explains the commands for group chat. http://empireminecraft.com/wiki/groups/