It's actually easier to enforce a noncompete in California on a founder or principal of a firm than it is on an employee. I don't recall the exact, legal specifics, but it has something to do with the fact that those people are in some way attached to the "goodwill" of the original business, which is something of value that the company can protect.
Someone else can probably say it better than I can, but that's how I understand it at this moment.