The famous legal theorist Ronald Dworkin once claimed that the most meaningful contact the average person will have with the law over the course of a lifetime is his or her day in court. I suspect those words ring true for Sheena and Tiara Yates, the lesbian couple from New Jersey who now find their most intimate decisions at the center of a sure-to-be-precedent-setting appeal about sperm donor visitation rights.

The couple used a sperm donor who signed an agreement in which he relinquished the right to visit “his” child. When the child was born, however, the donor changed his mind, and is now suing the Yateses, seeking to secure the legal right to visit the child.

According to Andy Polhamus, a reporter with the South Jersey Times, the couple’s young son was conceived by “at-home artificial insemination.” The euphemistic restraint of that phrase is admirable. The decision not to speculate on the precise sexual logistics of an “at-home artificial insemination” would read as a fine example of journalistic propriety. However, New Jersey law places a great deal of emphasis on the exact method by which a child is conceived. The state’s artificial insemination statute specifies that a non-biological parent, such as Ms. Yates, is considered a child’s legal parent only when the artificial insemination happens under the direct supervision of a physician.

Although Ms. Yates and her wife consulted with a doctor before the artificial insemination, the doctor didn’t directly supervise the requisite actions. That medico-legal technicality is the sum total of the reason they’re in the protracted court battle they’re in now, a position where an appellate panel’s ruling will have a direct and profound impact on their lives, not to mention the lives of thousands of other lesbian couples in similar circumstances.

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What about that contract? The Yateses had a binding contract and yet they lost in the New Jersey Superior Court (leading to their current appeal). What gives? The Superior Court judge ruled that, despite the contract, the sperm donor was the child’s legal father. He was, therefore, presumptively entitled to visitation rights, provided that visitation would be consistent with “the best interests of the child.” Under New Jersey law (and the laws of many other states), however, the court’s refusal to enforce the contract is not a surprising result.

One tends to assume that a contract—proof that one knowingly and voluntarily gave up one’s right to visitation—should settle the dispute. It’s certainly what they assumed. “We just assumed that if we had a contract, these guys would be donors and nothing else,” Tiara Yates told the South Jersey Times. There is, after all, something final about signing a contract; they exist to bind.

Moreover, even had the Yateses read the law, they might have been forgiven for thinking that a written contract would help. In 1990, when assisted reproductive technologies were growing in popularity (the first baby born by in vitro fertilization, Louise Brown, was born in 1978), the radical feminist magazine Off Our Backs ran a story about one of the Supreme Court’s early decisions on sperm donor visitation rights. The Supreme Court, then under the leadership of Chief Justice William Rehnquist, declined to hear an appeal from a ruling by the Oregon Supreme Court. By declining to take the case, the court strongly implied—and, for all practical purposes, decided—that sperm donors should be allowed to sue for visitation rights. The Oregon court had ruled that the right to seek visitation over one’s biological progeny was protected by the  Due Process Clause, sperm donor or not.

However, in that case, there was no contract. Quite the opposite: the donor-father claimed that all parties had agreed that he would remain active in the child’s life, including having input on the child’s religion and education. Off Our Backs’ anonymous author, “ls,” counseled would-be couples: “The case indicates the importance of written agreements to protect all parties.” It’s hard to say that it was an unreasonable conclusion.

But it’s not so. Shockingly, personally, even painfully not so, as couples like the Yateses are now finding out. A contract—one’s name in ink at the bottom—is not enough.

However, cases involving sperm donors are not the only ones where US family law regards bona fide contractual consent as inadequate. When there are living, breathing children involved, our law becomes considerably more lenient about the idea that one’s word, once given, is one’s more or less irrevocable bond. In cases of adoption, for instance, many states allow the new mother to revoke her freely given contractual consent for a specified amount of time (up to several months) after the child is born. Still other states, even more paternalistic, enforce a “waiting period”—typically around 72 hours—before the mother’s consent to adoption can be legally given. There’s a sense that certain choices—choices involving children—are of such gravity that we ought to have the opportunity to back out of them, that there ought to be some wiggle room when the potential cost of a mistake is lifelong regret.

So, it seems, we have to ask: Is a sperm donor any different? Should he be able to escape from a contractual promise?

New Jersey courts (and the courts of other states) have already ruled that a contract is not enough in the case of a surrogate mother. The famous case of “Baby M” decided that, despite the existence of a surrogacy contract containing a waiver of visitation rights, a surrogate mother is a child’s legal mother (and therefore presumptively entitled to visit). Later decisions, such as the case of A.G.R. v. D.R.H & S.H., clarified that it doesn’t matter whether the surrogate mother is also the egg donor.

But it’s not clear that a sperm donor is in the same position as a surrogate mother. While the child might be made from his genetic material, at no point does he have to literally bear it inside him. This seems to be a case where men and women, owing to biological differences between them, are not similarly situated.

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Perhaps the most remarkable aspect of the Yateses’ case is that the two women recently became legally married. New Jersey has allowed same-sex marriage since October 2013, when the state’s ban on gay marriage was invalidated by judicial decision.

The fact of their marriage is interesting not only because its very existence is a recent invention, but because, traditionally, marriage affords children born to the married couple certain protections. Among these is the common-law presumption that a child born to a married woman is her husband’s. This presumption shouldn’t be over-read. It doesn’t mean, for example, that an extramarital lover can never establish paternity—e.g., by blood or DNA evidence. Rather, it grants couples two weaker protections. First, doubts about paternity will be resolved in favor of the husband. And second, after a certain amount of time has passed since childbirth (two years is typical), the husband’s paternity can no longer be legally challenged.

Given its gendered language—i.e., the explicit reference to a husband and wife—you would think that this presumption wouldn’t (or couldn’t) apply to a lesbian couple. As law professor John Culhane, writing for Slate, put it: “A mater isn’t a pater.” But that too-neat semantic argument merely begs the question. Why shouldn’t the presumption, a privilege of marriage, be re-conceptualized to extended to same-sex couples?

That’s the argument—or one of the arguments—the Yateses plan to press on appeal. Since same-sex couples are now equal, their lawyers will say, they should be allowed to rely on the presumption as well.

This presumption was invented (in whatever sense it may be said that legal doctrines are “invented”) in an era before blood and DNA testing existed. It was a response to the practical and social problems of establishing paternity. We needed some way to decide who would reap the benefits (like visitation rights) and bear the burdens (like child support) of fatherhood. So we decided that, in general, it was socially expedient—and, in most cases, safe—to assume that a baby born to a married woman was her husband’s.

Although this presumption may seem to have been outmoded by technologies, such as DNA testing, that can establish paternity definitively, the Supreme Court ruled—in the famous case of Michael H. v. Gerald D. (1988)—that the presumption is constitutional. In that case, Gerald D.’s wife gave birth to a child. More than two years after the child’s birth, Michael H.—a man with whom the wife had had an affair—came forward claiming to be the real father. He sought visitation rights, armed with blood tests and other evidence.

At the time, however, California law specified that challenges to paternity could only be made within the first two years of the child’s life. And it had, as I mentioned, been more than two years. Michael H. challenged that result—he was, after all, probably the child’s biological father—arguing that this California law was unconstitutional, since it deprived him of due process and his right to see his child. The Supreme Court, however, did not agree with Mr. H. In a 5–4 decision, opinion by Justice Antonin Scalia, the court ruled that the California law was constitutional. The couple and the child, Scalia wrote, had rights, too, including the right to have the matter settled after a certain amount time. So, the presumption trumped. Mr. H. had waited too long to come forward with his evidence of paternity.

What should we make of all this? Should same-sex couples get the benefits of the presumption? Is it discriminatory to deny it to them? Slate seems to think so; they ran John Culhane’s article with the subheading: “Marriage equality isn’t enough to protect gay families.” And it’s certainly true that the Yateses’ case illustrates one of the many ways in which affording same-sex couples the right to marry doesn’t—can’t—resolve all the thorny questions same-sex relationships raise.

At the same time, it’s far from clear that extending the presumption of paternity—or, let’s call it “the presumption of legal parentage”—to same-sex couples is the best solution. After all, in cases like the Yateses, there’s no ambiguity about who the child’s biological father is. It’s the sperm donor. One can imagine other, more complicated cases where the presumption might be useful—say, one in which a bisexual woman using a sperm donor to conceive with her lesbian partner also has an affair with a man. But where, as here, there’s only one man involved, the animating rationale for the presumption simply doesn’t apply. There’s no question about who the biological father is.

In addition, the Supreme Court’s decision to uphold the presumption in the Michael H. case was premised on there being a time period (those two years) during which paternity could be challenged. That much time hasn’t passed for the Yateses, so it’s not clear that applying the presumption to foreclose the donor from seeking visitation rights would be constitutional.

In short, chances for the Yateses’ lodestar legal argument about marriage equality—the one that’s attracting so much media attention—are slim.

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The Yateses’ case is compelling because it requires us to introspect. About what parenthood means. About what the rights of same-sex couples who use assisted reproduction—which many inevitably will—should be. About how far the freedom of contract should extend. And about how we define the rights and obligations that go hand-in-hand with one’s reproductive abilities.

However engaging it may be to debate those philosophical questions, achieving fairness for same-sex couples likes the Yateses seems to have an easy legal solution: enforce the contract. The only barrier to doing so is New Jersey’s artificial insemination statute, the one requiring that same-sex couples perform artificial inseminations under a physician’s direct supervision if they wish to have their partners be regarded as legal parents. That’s an essentially arbitrary rule. It’s the result of a puritanical squeamishness whose consequence is to treat people with identical intentions differently based on whether they can afford—or whether they want to use—a doctor to carry out the artificial insemination. As law professor Kimberly Mutcherson noted, the law favors those who can afford anonymous sperm donors and cryo-banks over lower-income people who choose at-home artificial insemination.

It’s regrettable that such a trifling distinction should decide whether a contract about visitation rights—a voluntary agreement between knowing adults—will be enforced. Here’s hoping New Jersey’s Superior Court sees through the political and philosophical snarls and prevents the harsh consequences this law could have for well-meaning people like the Yateses.