Donald Trump recently made headlines by announcing a plan to give new mothers six weeks of paid maternity leave. Government-mandated family leave benefits are likely to hurt female workers more than they help them because they limit their choices and make it more costly for employers to hire women of childbearing age, thereby incentivizing businesses to hire fewer of them. This is true even if the benefit is paid for by the taxpayers rather than employers, since the latter will still bear the cost of having workers absent for a number of weeks. Some critics also claim the plan is based on sexist assumptions. But it has an even more basic flaw: under longstanding Supreme Court precedent, it is unconstitutional.

The maternity benefit will only be available to women with children, not men. Trump’s own website states that the proposed benefit is for “new mothers,” without mentioning fathers. Since the 1976 case of Craig v. Boren, the Supreme Court has ruled that laws that discriminate on the basis of sex are presumptively unconstitutional. They will only be upheld if they are “substantially related” to an “important state interest.” In more recent cases, the Court has made clear that this “intermediate scrutiny” is very rigorous, and that rough statistical generalizations – such as claims that women, on average, need parental leave more than men do – are not enough to satisfy the standard. Discriminatory laws cannot be based on “fixed notions concerning the roles and abilities of males and females,” even if those notions have some statistical support.

It does not matter whether the law in question discriminates against women (as most sex-discriminatory legislation did in earlier eras), or against men, as in this case. Both kinds of discrimination are subject to the same rigorous heightened scrutiny. The Oklahoma law struck down in the Craig case also discriminated against men: under it, 18- to 20-year-old men, but not women of the same age, were forbidden to buy 3.2% beer. Heightened scrutiny also applies regardless of whether the discriminatory law is motivated by sexist prejudice. Even well-intentioned discrimination is presumptively unconstitutional – and for good reason. History shows that seemingly “benign” race and sex discrimination by the state often causes great harm. Finally, the Court has also made clear that the same standards apply to discrimination by federal government, as by the states.

One legal commentator suggests that Trump’s policy might survive legal challenge based on 1970s decisions holding that discrimination on the basis of pregnancy does not qualify as sex discrimination. But Trump’s plan does not discriminate between people who are pregnant and those who are not. It discriminates between new mothers and new fathers. It is not a law that, as the Court put it in a 1974 ruling, classifies on the basis of the “physical condition” of pregnancy and thereby avoids “discrimination based upon gender as such.” A law that creates a benefit for new mothers but not new fathers clearly does “discriminate based upon gender as such.” Given the existence of adoption and surrogacy, a substantial number of mothers are not even people who have just gone through a pregnancy.

In sum, if Trump’s maternity leave plan were ever enacted into law, it would likely be struck down by the courts as unconstitutional. Trump has demonstrated utter contempt for constitutional rights and limitations on government power on a shockingly wide range of issues. His discriminatory maternity leave plan is another addition to a troubling list.