As far as sueing goes, a group of girls couldn't really sue a local panhellenic for denying NPC expansion, because no NPC group (even if they were dying to colonize) would stand behind the interest group sueing. All NPC members have agreed only to colonize when invited, and wouldn't pursue legal action if they weren't. An interest group could sue to have a local or non NPC affiliated national installed because that group wouldn't be held within NPC guidelines and a vote of expansion wouldn't be required in the first place. I hope that makes sense, I could be confused though.