I was under the impression that non-competes were legally implemented not to stop employees moving, but to stop an owner from selling a business with goodwill, and then starting up a competitor across the road and reducing the goodwill be retaining their old customers. I have no evidence, but had assumed that the modern non-compete enforced on employees by employers came out of a precedent based on this law and has slowly gained acceptance. Happy to be educated if somebody knows more.