Originally Posted by DrHax

Treat this Clan War like you would a duel: Take screenshots, save chat logs, and if you can: save replays. The more evidence the better.

If you find a GM online, they don't hold an obligation to referee the match, but you're more than welcome to asking them. They might ask in the GM channel if there's someone available. At the very least: someone on IRC would be useful for both teams in case anyone has questions about the rules mid-war.