What type of value is PoleKeeper?
The entire GUILD owns the pole not just one client...and seeing as it's part of the guild class (according to your example) it's not a guild... is it a bool or something?
For my system I'm having the guildwar class hold a guild structure which is the 'current pole owner' which by default is null...
Then in the sob attack checks or w/e I simply do...
if(GuildWar.WinningGuild != null && GuildWar.WinningGuild == user.Guild)
Do action check is needed for.
Handling who is winning is not a complex thing to do but I've seen it done so very many ways in different servers.