Various states are considering child custody reform. For example, here is a recent Michigan proposal. The idea is that the legislature would require the family courts to start with a rebuttable presumption of shared child custody in divorce cases.
The opposition comes from lawyers, feminists, and others. The lawyers don't like shared custody because it reduces the need for litigation. They'll argue that every case is individual and that judges need maximum discretion because then lawyers are needed for a high-stakes court dispute. The feminists want women to be in charge and to get more support payments, and they get that when mothers get primary custody. Various others profit from a bias towards mother custody, because it maximizes the transfer payments.
There are also some conservatives who oppose shared custody, and that is harder to understand. I will look at specific arguments from them. (These arguments are taken directly from a private letter, but I am not at liberty to post it.)
Argument: Most parents do not split responsibilities 50-50.
It is certainly true that mothers change most of the diapers, but parental responsibilities encompass much more than that. If a father works two jobs to support his family, and doesn't play patty-cake with his kids all afternoon, then are you going to say that he is not living up to his responsibilities?
In my experience, most parents do split their parenting responsibilities fairly evenly. They don't take identical roles, for various reasons, but they both contribute in crucial ways. It is only by devaluing the father's role could anyone say that the mother performs 85% of the parenting responsibilities.
Argument: Shuttling kids is not conducive to order and stability
The order and stability that kids crave is having two parents who are integral parts of their lives. They are much more attached to their parents than their beds. Those who argue for mother custody often talk about how a child may be attached to her toys and dolls, but the argument depends on the notion that a child's attachments to some material things is more important that her attachment to her parents. They are not.
Some divorced parents hand off their kids daily; some do it weekly; and some use other schedules. Shared parenting does not have to necessarily follow any particular schedule. Some schedules actually involve less shuttling that the typical mother custody arrangement in which the father gets visitation every other weekend.
Sometimes there are complaints about the "dangers of lost homework", but the empirical evidence is that kids do better in school when fathers share custody, than when raised by single mothers. Problems coordinating things like homework are relatively minor compared to the enormous gains from having both parents actively raising the kids.
Argument: Shared custody is not in the best interest of the child
Some argue that judges need the discretion to award custody in the child's best interest, and that is usually not shared parenting. Anyone who thinks that judges are making decisions based on the best interest of the child (BIOTC) is delusional. BIOTC is just a buzz phrase that courts use to justify doing whatever they want to do. I defy anyone to show me one single case in the USA that was actually decided based on BIOTC.
I happen to be an expert in optimization theory. To determine the BIOC, one must, as a minimum: identify the interests of the children; adopt a methodology for measuring and consolidating those interests into a best interest; define the range of custody alternatives; and evaluate and compare those alternatives according to the consolidated best interest. These things are never done by the family court.
Argument: Fathers should get liberal visitation
This is perhaps the most offensive argument. Use of this language shows a refusal to accept fathers as having a true parenting role. Some mothers just want fathers to be visitors (and financial providers). They will let them be occasional babysitters, but not be the father figures that kids really need.
Children do best when they have a mother and a father, and when both the mother and father have genuine parenting roles.
Argument: Even Dobson's Focus on the Family is against shared parenting
James Dobson's Focus on the Family does indeed have a position paper against shared parenting. It is not clear exactly what the status of this position paper is, as it is undated, unsigned, unpublished, and not on Dobson's web site. I assume that the paper is authentic, but it may include views that Dobson is unwilling to put his reputation behind. You can find the position paper here, along with a good rebuttal by Dr. Fink.
As you can see from Dr. Fink's rebuttal, Dobson relies heavily on discredited research from Judith Wallerstein. Wallerstein's so-called research has done a lot of damage. She wrote (about her own work): "Research by Drs. Judith Wallerstein and Joan Berlin Kelly revealed that approximately 50 percent of mothers either saw no value in the father's contact with his children and actively tried to sabotage it, or resented the father's contact." (Wallerstein, Surviving the Breakup, HarperCollins, 1996, p.125).
Similar opinions by Wallerstein persuaded the California supreme court in 1996 to allow custodial parents (usually the mothers) to move their children permanently away from the fathers for just about any reason. Her arguments to the court are rebutted here: The Burgess Decision and the Wallerstein Brief, by Richard A. Gardner. M.D., Journal of the American Academy of Psychiatry and the Law, 26(3):425-431, 1998.
Contrary to Wallerstein's opinions, the scientific research studies show overwhelmingly that shared custody works better than mother custody. Dobson's paper tries to down play Bauserman's meta-analysis because of non-uniformity in the cited studies, because some of the cited studies were unpublished Ph.D. theses, and because some of Bauserman's other research has been disturbing. But Bauserman's results have been confirmed by everyone who has looked. See for example, Father and Child Reunion by Warren Farrell (Penguin, 2001). Farrell looked at studies that tried to measure child custody outcomes a dozen different ways, and found that shared parenting did better than mother custody on every single one. He persuasively explains just why fathers are so important to their children.
It is baffling how any pro-family organization could be against shared parenting. The law should minimize the incentives for divorce, and it should help maintain family relationships to the extent practical. With today's unilateral divorces, any spouse can get divorced at any time for any reason, but there is no reason why the court should step in and effectively divorce the kids from one of the parents.
Conservatives should also oppose the intervention of judges into routine child-rearing decisions. That is what usually happens now when there is a custody trial or any other court procedure that is supposedly based on the BIOTC. Conservatives should favor leaving those decisions in the hands of the parents. And I mean both parents. The courts should not interfere unless there is criminal child abuse or something like that. Conservatives are adamantly against government interference in child-rearing by a married couple, and they should similarly object to interference with a divorced couple. The surest way to accomplish that is to have a statutory presumption of 50-50 custody.
Even the US Supreme Court has repeatedly declared that parents have a fundamental constitutional right to make decisions concerning the care, custody, and control of their children. This was reaffirmed as recently as 2000 in Troxel v. Granville.
In sum, a presumption of shared custody is the best way, whether one looks at empirical evidence, conservative values, or what is good for children.