One of the lingering questions teed up by Justice Scalia’s dissent in Lawrence v. Texas, and left unresolved, is whether the state has a compelling interest in banning adult incest, where all parties are of age and consent to the relationship. This question has come to the fore after a jarring report that a daughter is in a sexual relationship with her father (the mother does not know). The daughter acknowledges that they would not get legally married, but they seem intent on continuing to have sexual relations. And, the daughter indicated that she wants to move to New Jersey where adult incest is legal (it seems the Garden State forgot to pass that bill). In response, New Jersey legislatures want to pass a bill criminalizing adult incest.

The bill would make it illegal to marry or commit an act of sexual penetration with a blood relative, including half-siblings. Violators could face three to five years in prison and a fine of up to $15,000.

Angelini, a Republican from Monmouth County, said adult incestuous relationships “violate our acceptable moral standards” and often involve sexual abuse that is blurred by the “consensual” loophole.

Would such a bill be constitutional? Under Lawrence v. Texas and Windsor, I think the answer has to be no.

First, the father and daughter are both consenting adults who claim to love each other, and enjoy sexual relations with each other. Why should the state have any interest in their private lives. They aren’t even seeking any recognition of their relationship.

Second, as we learned in Windsor and its progeny, the state has no compelling interest in encouraging responsible procreation. That incestuous relationship may yield children with birth defects, under strict scrutiny, is not a sufficient reason to stop them from cohabitation. As the daughter points out in that article, the state allows people who carry dangerous recessive genes–such as Tay Sachs–to have sex and marry. Perhaps a blanket ban on incestuous relationships could serve as a prophylactic against passing on recessive genes. But if that were the case, testing the couples would seem far less invasive than criminalizing the ban. Although, the state would have no similar interest in banning same-sex incestuous relationships, because there is no possibility for offspring. The state’s strongest interest involves the risk of sexual abuse with incestuous relationships. But both parties are consenting adults, and are presumed competent to engage in many sexual relationships that may not be healthy. Criminalizing all aspects of sexual relationship between blood-relatives who consent would seem to be overbroad, under strict scrutiny, in the absence of compelling evidence that a blanket ban is justified.  Perhaps a background check for domestic violence must be performed before issuing such a license. (If you think this is absurd, let’s talk about licensing another constitutional right that appears right  below the First Amendment).

Third, we learned in Windsor that traditional notions of morality are grounded in animus, and do not provide a valid basis for infringing on personal relationships. The New Jersey legislator said as much: adult incestuous relationships “violate our acceptable moral standards.” That’s a per se violation of the principles of Romer.

Fourth, to the extent that we look abroad to international law to inform evolving standards of decency, experts in Switzerland and Germany have proposed decriminalizing adult incest. The German Ethics Counsel offered these thoughts:

But on Wednesday, the German Ethics Council recommended the section be repealed, arguing that the risk of disability in children is not enough to warrant the law and de-criminalising incest would not remove the huge social taboo around it.

The chairman of the council, Christiane Woopen, was among the 14 members voting in favour of repealing section 173, while nine people voted for the ban to continue and two abstained.

A statement released on Wednesday said: “Incest between siblings appears to be very rare in Western societies according to the available data but those affected describe how difficult their situation is in light of the threat of punishment.

“They feel their fundamental freedoms have been violated and are forced into secrecy or to deny their love.

“The Ethics Council has been told of cases where half-siblings did not grow up together and have only met in their adult lives.” …

“The majority of the German Ethics Council is of the opinion that it is not appropriate for a criminal law to preserve a social taboo,” it added.

“In the case of consensual incest among adult siblings, neither the fear of negative consequences for the family , nor the possibility of the birth of children from such incestuous relationships can justify a criminal prohibition.

“The fundamental right of adult siblings to sexual self-determination has more weight in such cases than the abstract protection of the family.

Although, the Germans only recommended eliminating the ban between siblings, not between parents and children. So maybe the daddy-daughter date is out of luck.

And if siblings are allowed to have sexual relationships, why shouldn’t they be able to receive a marriage license. Why should the government deny them a license if the couple asked for one? Granted, there is no social movement pushing for incestuous marriages, like there is for same-sex marriage. Further, to my knowledge, no other states are moving to eliminate bans on incest. So perhaps, in this sense, federalism counsels against uprooting incest laws.

If you couldn’t tell, this post was somewhat tongue in check. None of this is to suggest the Court should uphold the same-sex marriage ban. Rather, I write this to suggest that this is going to be a much harder opinion to write than people appreciate. There’s a big difference between a circuit court opinion which people will soon forget (even Judge Posner’s), and a Supreme Court decision that will affect all 50 states, invalidate dozens of state constitutional provisions, and live in perpetuity in the U.S. reports and case books. Whatever the majority opinion is will have to contend with these arguments. The Court ducked the question in Lawrence and Windsor, but if they reach the merits, they will have to explain why incest laws remain constitutional. Scalia’s dissent, at last, will have to be addressed.