California Code, Family Code - FAM § 4613

(a) The obligor-parent is not receiving salary or wages subject to an assignment pursuant to Chapter 8 (commencing with Section 5200) and there is reason to believe that the obligor-parent has earned income from some source of employment.

(b) An assignment of a portion of salary or wages pursuant to Chapter 8 (commencing with Section 5200) would not be sufficient to meet the amount of the support obligation, for reasons other than a change of circumstances which would qualify for a reduction in the amount of child support ordered.

(c) The job history of the obligor-parent shows that an assignment of a portion of salary or wages pursuant to Chapter 8 (commencing with Section 5200), would be difficult to enforce or would not be a practical means for securing the payment of the support obligation, due to circumstances including, but not limited to, multiple concurrent or consecutive employers.