I have no stake in this so perhaps it is easy for me to make comments but here it is: if nobody agrees that there is any value in this currency then there is no value even if real money is involved. I could have written this a little bit better, I know.

So a hard fork is in essence the community saying that they do not accept that there is any value for them beyond a certain point. Nobody breaks any laws. The "attacker" can retain what they gained. Nothing changes. The community simply moves on to another island - it is as simple as that.

I am not a lawyer but I cannot see how someone can sue you for not wanting to do business with them purely from value perspective. Perhaps this is a bit of an extreme example but it is also as if I start suing everyone because they do not accept doing business with me while I pay them with seashells (once perhaps considered a valid tender).