Are you referring to a lawsuit for the decision that a JC makes or for the actual Judicial Committee practice?
The most likely place to file this kind of suit would be in the US because in the US there is a lot more latitude on what you can file a civil suit for and how much you can win in a civil suit. Most of the rest of the world the government limits what you can sue for and the winnable amount of damages that are winnable.
On the whole shunning issue that is pretty much an unwinnable case thanks to Serbian and the Paul decisions. But it would be interesting to see if someone went the other route and tried to sue over the actual Judicial Committee process. It would be really hard to win, your either going to have to have a lot of disposable income, find a lawyer who will take a huge percentage because they will be having a huge risk of winning nothing or you just file in small claims court for the statutory maximum.
That would be an up hill battle but hey in the US you can sue for anything.