Contemporary American law is increasingly committed to a project of sex enforcement. Across statutes, executive orders, and litigation positions, governments define “biological sex” as binary, immutable, and determinable at birth. They then use that static, dimorphic model to regulate people’s access to rights, spaces, and services. This Article argues that this project has a devastating and largely unacknowledged collateral consequence: the rhetorical and practical erasure of intersex Americans. Intersex variations—naturally occurring differences in sex characteristics—demonstrate that sex is not a single binary trait but a multi-factor biological phenomenon that does not reliably sort human bodies into two mutually exclusive categories. Because intersex variation makes binary classification scientifically unstable and administratively unworkable, contemporary sex-binary regimes must treat intersex bodies as anomalies, exceptions, or errors rather than as ordinary human variation.
This Article traces the rhetorical shift that enables this project, showing how “biological sex” has been deployed to cast sex binarism as objective reality rather than ideological belief. It then provides an overview of the biology of sex differentiation, explaining how chromosomal, gonadal, hormonal, anatomical, and secondary sex characteristics vary independently across individuals, and demonstrating that intersex variations are neither rare nor anomalous. It shows that no single biological marker—and no combination of markers—can coherently sustain a binary definition of sex. The Article examines how states and the federal government nonetheless codify binary sex through statutory definitions, executive orders, and litigation rhetoric that render intersex people legally unintelligible. The Article maps the consequences of that illegibility across healthcare, identity documents, sex-segregated spaces, education, and athletics. In the healthcare context, this Article examines a core policy conflict: bans on gender-affirming care for minors frequently prohibit medications and procedures for transgender adolescents out of purported concerns about irreversibility and the capacity of transgender youth to consent while expressly permitting surgical and hormonal “normalization” interventions to “treat” or “correct” intersex infants and small children. Finally, the Article argues that these contradictions reveal the deeper function of contemporary anti-trans policy: not the protection of children or medical ethics, but the enforcement of binary sex as a governing legal order. It concludes by assessing the resulting doctrinal landscape and identifying potential strategies—grounded in consent doctrine, equal protection, and related constitutional theories—to challenge binary sex enforcement and to re-center intersex bodily autonomy in disputes over sex classification.
