In this excellent article from Coindesk US legal counsel set out the many complex legal challenges that potential plaintiffs may face should they suffer economic loss due to a hard fork.
What’s a hard fork and what’s the issue?
Bitcoin is suffering from growing pains (scaling issues), the pain is in the form of longer transaction confirmation times and increasing transaction costs. There are two main groups debating a solution to the problem, the original bitcoin developers, called bitcoin core and a new group, called bitcoin unlimited.
The hard fork refers to a situation where the groups cannot agree and we end up with a split (hard fork) and two versions of bitcoin (bitcoin 1 and bitcoin 2), obviously a very disruptive event and bitcoin holders may suffer economic loss.