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.
Nope, provisions for that are in M&A agreements and part of the reason why acquiring companies takes so much money and [lawyer]time. And it's in no way a "precedent based on this law" - what do you mean by "this law"? All of these provisions are in private contracts, not in legislation.
The classic use of non-competes is for salespeople or high-level service people (lawyers, consultants, etc) not taking their customers with them when leaving.
I don't know the history but if that were the case then the non-compete should be between the owner and buyer, not employer and employee. It makes no sense to go after the employees to prevent former owner competition.
Those are one of the few types of non-competes that are enforceable in California. Otherwise, the majority of non-competes in America, by raw count, are not about owners selling the company.