Consider an example: The mother has been a girl's primary caregiver, but is planning to teach the daughter racist views. The father hasn't been the primary caregiver, so the daughter would have some trouble (though not a vast amount) adjusting to being raised by the father. But the father would raise her to be tolerant, which will likely make it easier for her to live a well-adjusted and law-abiding life, perhaps make her a happier child, and definitely make her a better person.

If a judge were to consider all the facts, he might well find that the child's best interests would be better served by giving the father custody. If, however, the First Amendment barred the judge from considering the mother's likely future speech, then the mother would get custody. Such a First Amendment rule would thus lead the judge to make a decision that's not in the child's best interests.

But while accurate decision-making is usually good, the government must sometimes sacrifice some such accuracy, at least so long as the sacrifice doesn't yield very grave harms. Consider Palmore v. Sidoti, where the Court held that the Equal Protection Clause barred family courts from considering a parent's new interracial relationship in the “best interests” analysis. The Court acknowledged that “a child living with a stepparent of a different race may be subject to a variety of pressures and stresses not present if the child were living with parents of the same racial or ethnic origin.” Giving custody to the interracially involved parent may thus have been against the child's best interests. But the Court nonetheless held that “[t]he effects of racial prejudice, however real, cannot justify a racial classification.” The Constitution, in the Court's view, required that courts refuse to consider certain evidence, even when that evidence was relevant to the best interests inquiry.

And while excluding speech from the analysis is likely to lead to some suboptimal results, it's unlikely to lead to the downright awful ones: If our hypothetical mother is likely to be physically abusive or neglectful, and not merely racist, then the custody decision will go against her even if her constitutionally protected speech is excluded from the best interests analysis.

True, excluding the speech may risk some harm to the daughter, for instance by making her more likely to get into fights, or potentially reducing her educational and employment prospects. Yet this is a risk we tolerate for children being raised by intact families. The parent's constitutional rights, and society's constitutional interests in preserving parent-child speech from government restriction, justify protecting parents' speech rather than focusing solely on the children's best interests. The situation should be no different when the family is split.

4. Government Intervention in Divorce Reducing the Marginal Cost of Further Intervention: Some argue that we don't want the government to intervene in intact families because such intervention is too harmful to such families, and to their children -- “[t]he remedy would be worse than the disease.” But, the argument goes, once at least one of the parents has called in the courts and some intervention is therefore inevitable, the extra level of government intrusion “adds no disruption to a family that has already broken up.”

Yet this isn't quite right. Even in intact families, we distinguish types of intervention: Laws restricting child abuse, child labor, and the like do indeed intrude on parental decision-making, but they're allowed. But laws restricting what parents in an intact family teach their children are forbidden, because restricting parental speech is more intrusive than restricting parental beating or even parental decisions about the child's employment.

Likewise, when a family is split, the government must step in, and this inevitably involves some intrusion and disruption. But government decisions that restrict a parent's speech are even more intrusive -- and even more disruptive to an honest relationship between the parent and the child -- than is the government's decision about who is to have custody that is based solely on the parents' nonspeech conduct.

5. Protecting the Other Parent's Ability to Control What the Child is Taught: Parents are legally empowered not just to teach their children, but to keep others from teaching the children things the parents dislike. Of course, no parent can keep the child completely insulated from contrary speech, especially as the child gets older. Yet much teaching requires time and repetition. By controlling which school or church children go to, influencing which children and adults they spend time with, and influencing which media they read and watch, parents can substantially control their children's moral and ideological influences.

In intact families, both parents have the right to teach their children what each of them pleases. But in split families, one parent may want to stop the other parent from, for instance, teaching a child a religion or political ideology that differs from what the first parent is teaching. The parent may argue -- as one New Jersey appellate court actually held -- that “[i]t is implicit in protecting the primary caretaker's right to raise and educate his children in his chosen religion to prevent others from simultaneously educating the same children in an alternate religion.”

Yet while many parents sincerely want to stop the other parent from teaching the child certain views, it's hard to see why this desire should be given the force of law. When two people have a child together, each must reasonably expect that the child will be exposed to the other's teachings, including teachings that might change over time. There's no reason why the breakup should increase one parent's control rights relative to what they were before the breakup, and thus decrease the other parent's speech rights.