That's what Ryan Anderson says in his new book--Truth Overruled: The Future of Marriage and Religious Freedom (Regnery Publishing, 2015)--which is a critique of the Supreme Court's decision in Obergefell v. Hodges declaring that same-sex marriage is a constitutional right.
This remark by Anderson suggests that he would agree with my argument that marriage should be privatized in that marriage would be a purely private contract, and government would no longer issue marriage licenses. But then he contradicts this by arguing that government should give marriage licenses only to opposite-sex couples. Not only does he contradict himself, he also contradicts the equal protection clause of the Fourteenth Amendment of the Constitution by denying same-sex couples the "equal protection of the laws."
Here's the whole passage in which the above sentence appears (34-35):
Anderson ignores the “original meaning” of “equal protection." To give marriage licenses to heterosexual couples but not to homosexual couples violates equal protection unless there is some rational justification for this distinction. If the rational justification is that children are better off when both their biological mother and biological father care for them, then the states should prohibit same-sex couples, single parents, and stepparents from child care. If the risk to children is as a rule no greater with a same-sex couple than with a heterosexual single parent or heterosexual stepparents, as Anderson indicates (150-162), then denying a marriage license to the same-sex couple violates equal protection because there is no rational justification for this discrimination between homosexuals and heterosexuals. (Here I agree with William Eskridge--in his amicus curiae brief and in his recent article in the Cato Supreme Court Review--that the original meaning of equal protection would support the ruling in Obergefell but not Kennedy's reasoning for that ruling, which ignored original meaning.)
If the rational justification for denying marriage licenses to same-sex couples but not opposite-sex couples is that the state wants to promote families in which children are under the care of both their mother and their father, then the state should establish covenant marriage laws like those in Louisiana, Arkansas, and Arizona. Those couples with a covenant marriage license would be denied any right to a divorce except when they prove that one of the spouses is guilty of abuse, abandonment, or adultery. And, indeed, Anderson says that this has always been the best marriage law for promoting “real marriage” (39-41). Couples might be free to choose a marriage license that allowed for “no-fault divorce,” but the constitutional standard of equal protection would require that this kind of marriage license would have to be available for same-sex couples as well as opposite-sex couples. State law might identify the covenant marriage license as "real marriage" and the no-fault divorce marriage license as "romantic companionship," which would teach a clear lesson about the superiority of the one over the other.
If "real marriage" is rooted in natural law, and thus is not an artificial creation of positive law, then such marriage will stand on its own natural ground in the natural inclinations of human beings, without any need for governmental licensing that violates the Constitution's equal protection clause.