Following up on Is this legal?

That's certainly one approach.  However, this follow-up adds something very significant to the case, which is his employer's failure to put on the garnishment.  If that was a proper garnishment order, your ex's employer broke the law.

And I would get a lawyer, this time, and go after both of them, if that's the case.  As your in-court experience has probably already suggested, judges don't like people who disobey court orders.  With people involved in divorce or post-divorce cases, it's almost expected to happen at times, but for a company not directly involved to disobey is far worse.

You should repost this question in the divorce area to get some competent advice and get it from a lawyer actually licensed in California as the laws are different from state to state.

If it’s a significant sum of money then you should consider hiring a lawyer to get it straightened out. The court can award you your attorneys fees if the circumstances warrant which may be the case here.

Hope this helps and best of luck to you.