Legal Question in Family Law in California

There is no such code section, exactly. The Family Code sets forth what a court may consider in setting child support. The court is not allowed to consider other things. The only misconduct that is permitted to be considered is misconduct related to income, such as refusing to work, or colluding with an employer to understate income (under the table cash pay, for example). This is because child support is considered to be owed to the child, not the receiving parent. If the receiving parent is misbehaving in a way that affects the child, that is a separate matter from child support and needs to be brought up in an appropriate motion, not by reducing support.