Wasn't aware of this... got hit by it recently.. SE doesn't seem to care or won't do anything about it. GMs are left powerless, and devs don't even seem to want to acknowledge it. These are the offered solutions:

a) Hope 35 days pass without the person logging in.
b) Hope they don't steal/sell everything.
c) Hope they give control of your FC, house, and chest back... worth potentially hundreds of millions of gil.

If someone were to do the stuff from b) SE won't do a damn thing to them. According to GMs, they have no power to change what the development team views as "FC politics."