Excellent question. I don't have a solid answer, but slander and libel claims could form a civil case, while intimidation, physical threats and using social media to extort could be criminal. I would file both a restraining order and a temporary injunction.

Frankly, I'm concerned for small businesses and raise a flag on using reviews as a leading source of authority.

It's a broken system that Yelp (and other intermediaries) should definitely be held accountable for perpetuating.