Legal Question in Employment Law in California

Without reading the contract or knowing the surrounding facts, it is impossible to give a definitive answer to your question. But, generally speaking, contracts that prevent employees from engaging in a lawful occupation are voidable and unenforceable in California. However, there may be a contract between your employer and the client that prevents the client from hiring away employees from the company. Those contracts are enforceable. You should inquire of the prospective employer whether such an agreement exists before making your decision.

I agree that a review of the relevant contracts would be necessary to give a definitive answer. I also agree that there is clear law that precludes an employer from enforcing a contract that prevents you from engaging in a lawful occupation. Unless, however, your industry is so small that you could not "ply your trade" except by going to work for clients of your employer, limits on going to work for customers/clients of employers are often upheld. It ultimately turns on whether the restriction actually prevents you from engaging in your occupation, or only limits some of the people you can work for.