> If you sign a contract with your employee saying you won't do no-poaching then doing so would be a breach of contract obviously but that would be a specific use-case.

You contract is "employment law" + "your contract". I they don't agree with employment law they have to override it in your contract, in this case with a non-compete clause. If they don't, you have both agreed to the terms in "employment law" + "your contract".