There is no shortage of good reasons to oppose the proposed amendment to North Carolina’s constitution that would ban gay marriage in the state. There’s the matter, for instance, of its inherent bigotry, not to mention its essential redundancy (the state already banned gay marriage in 1996.) But in the run-up to the decisive May 8 vote, a burgeoning grassroots movement in North Carolina is offering an entirely different justification for opposing Amendment One. Rather than pointing to the blatant harm the amendment would inflict on homosexual residents of the state, they are highlighting the unintended consequences it will have for heterosexuals.

Among the leaders of the effort is UNC law professor Maxine Eichner, who has been arguing to anyone who will listen that the fallout from the bill is poised to be larger and more destabilizing than most voters, and many lawmakers, understand. According to Eichner, Amendment One threatens to create a host of problems for North Carolina because of the language used in its most pertinent passage—namely, the phrase that declares, “Marriage between one man and one woman is the only domestic legal union that shall be valid or recognized in this State.”

The root of the problem that Eichner foresees—and that she publicized in a 27-page legal analysis, and repurposed into op-eds, slideshows, and Cliff Note-style summaries—is that the amendment diverges from the language used in existing North Carolina marriage laws. The ban on gay marriage that passed in 1996, the Marriage Protection Act, was very specific in how it defined marriage: “Marriages, whether created by common law, contracted, or performed outside of North Carolina, between individuals of the same gender are not valid in North Carolina.” That reserved the possibility of legal recognition for heterosexual couples who weren’t technically married.

Amendment One by contrast uses an ambiguous term—“domestic legal unions”—that was intended to block the way for civil unions and domestic partnerships for homosexual couples. But it may also inadvertently rescind the legal status already granted to non-married couples who live together. As a result, the state may be forced to put a halt to the growing number of protections—ranging from domestic violence protections to children’s health insurance—that it currently offers to non-married couples, homosexual and heterosexual alike.

By Eichner’s count, the rights of the over 185,000 straight, cohabitating couples in North Carolina would be put in jeopardy; ninety-one percent of the couples that would be affected, she claims, are heterosexual. She’s careful to note that rights for non-married couples wouldn’t immediately be rescinded wholesale if the amendment is passed. But as Eichner put it in her November paper, the amendment’s phrasing “has never been used in any statutory law in North Carolina or interpreted by our courts, and which has never been interpreted by courts in any other state.” At the least, the amendment seems guaranteed to set off a furious set of court battles over its scope.