This paper considers the affect of amendments to state divorce laws that strengthen their joint custody preference. It does so in the context of suits by noncustodial parents challenging substantive custody standards not requiring equal custody at divorce. The complaint is that most custody laws, by using a best interests standard rather than equally dividing custodial time, violate substantive due process. Further, two states, Iowa and Maine, have recently amended their custody legislation to strongly presume joint physical custody. After setting out the constitutional problem and describing the legislation in some detail, this paper tests the effects of the change in the Oregon statutes. Policy-makers might well want to know how children fare under joint custody as opposed to other possible visitation arrangements. In other words, does the child\u27s best interests, the hallmark of most current statutes, itself require joint custody? Empirical results from a broad national survey suggest that a close relationship with a non-custodial parent is significant in relieving various kinds of negative outcomes for adolescents, but that frequent over night stays, beyond once or twice a year do not matter much. Policy-makers might also question whether the stronger legislative preference really increases joint custody awards. Does its requirement that mediation alternatives be suggested (and, in some cases, ordered) in fact increase the number of cases that are settled by mediation? Do judges sometimes prescribe mediation in cases that are inappropriate (such as those in which domestic violence orders have been entered)? Do children receive less child support under the new statutory scheme? Is there evidence that the process makes divorce less painful and less expensive? Empirical results on Oregon suggest that while even small statutory changes have large effects, they are not necessarily the ones that motivated the legislation. The broader goal here is to suggest that changes in family law, while often made, are seldom systematically assessed. Society needs such accountability, particularly when children are involved. I show one way it might be done