California Code, Family Code - FAM § 3766

(a) The employer, or other person providing health insurance, shall take steps to commence coverage, consistent with the order for the health insurance coverage assignment, within 30 days after service of the assignment order upon the obligor under Section 3764unless the employer or other person providing health insurance coverage receives an order issued pursuant to Section 3765 to quash the health insurance coverage assignment.  The employer, or the person providing health insurance, shall commence coverage at the earliest possible time and, if applicable, consistent with the group plan enrollment rules.

(b) If the obligor has made a selection of health coverage prior to the issuance of the court order, the selection shall not be superseded unless the child to be enrolled in the plan will not be provided benefits or coverage where the child resides or the court order specifically directs other health coverage.

(c) If the obligor has not enrolled in an available health plan, there is a choice of coverage, and the court has not ordered coverage by a specific plan, the employer or other person providing health insurance shall enroll the child in the plan that will provide reasonable benefits or coverage where the child resides.  If that coverage is not available, the employer or other person providing health insurance shall, within 20 days, return the assignment order to the attorney or person initiating the assignment.

(d) If an assignment order is served on an employer or other person providing health insurance and no coverage is available for the supported child, the employer or other person shall, within 20 days, return the assignment to the attorney or person initiating the assignment.