The Numerus Clausus of Sex Sonia K. Katyal† There is a fundamental revolution under way regarding the relationship be- tween gender and the state, both domestically and internationally. Across the world, the rise and visibility of transgender rights movements have forced a persis- tent rethinking of the cornerstone legal presumptions associated with science, sex, and gender. As many people, along with multiple courts, colleges, and workplaces, now recognize, the binary presumptions of male and female identity are largely outdated and often fail to capture the complexity of identity and expression. The question for legal scholars and legislatures is how the law can and should respond to this complexity. Taking this observation as an invitation, this Article provides a different way to conceive of the relationship between sex and gender that might provide another vantage point in demonstrating the limits of our jurisprudence. Drawing on Pro- fessor Cheryl Harris’s groundbreaking article exploring whiteness as property pub- lished in the Harvard Law Review over twenty years ago, this Article argues that, in order to understand the relationship between sex and gender, it might be helpful to explore a parallel type of affiliation between identity, property, and intellectual property. My thesis is that sex is to gender as property is to intellectual property. Unpacking this further, this Article argues that, instead of thinking of sex as a con- struct of biology alone, it might be helpful for us to reconceptualize state-assigned † Chancellor’s Professor of Law, University of California, Berkeley, School of Law. The author wishes to thank the faculties of the University of California, Berkeley, School of Law; Boston University; the Williams Institute at the UCLA School of Law; Rutgers Law School; Fordham University School of Law; Seton Hall University School of Law; Maurice A. Deane School of Law at Hofstra University; the University of Washington School of Law; and the University of Miami Law School for helpful conversation. I am especially indebted to Kathryn Abrams, Kenny Alston, Sergio Campos, Mary Anne Case, Paisley Currah, Katie Eyer, Sheila Foster, Katherine Franke, Mary Anne Franks, Andrew Gilden, Zil Goldstein, Gayatri Gopinath, Joanna Grossman, Bruce Hay, Tracy Higgins, Clare Huntington, Molly Van Houweling, Neal Katyal, Alexander Lee, Linda McClain, Melissa Murray, Russell Robinson, Juana Maria Rodriguez, Darren Rosenblum, Simone Ross, Dean Spade, Edward Stein, Leti Volpp, and the editors of The University of Chicago Law Review for their insights and suggestions. I am also particularly grateful for the in- credible research assistance of Juli Adhikari, Joseph Galvin, Andrea Hall, Kelly Herbert, Nicole Rivera, and Catherine Song. 389 390 The University of Chicago Law Review [84:389 sex along the lines of tangible property—bordered, seemingly fixed, rivalrous, and premised on a juridical presumption of scarcity in terms of its rigid polarities of male and female. In contrast, regarding gender, I argue that thinking through gender as a performance, if taken seriously, also suggests that gender is more akin to intellectual property—permeable, malleable, unfixed, nonrivalrous—and ulti- mately deeply nonexclusive. Normatively, I argue that a model of gender pluralism is an important framework with which to examine the importance of gender diver- sity and fluidity. INTRODUCTION .................................................................................................... 390 I. SEX AS SCARCITY .......................................................................................... 400 A. The Ascriptive Function of Assigned Sex .......................................... 406 B. The Allocative Function of Assigned Sex ........................................... 411 C. The Evolution of the “Properties” of Gender...................................... 416 D. The Path of Transgender Jurisprudence ........................................... 423 E. The Legal Presumption of Polarity .................................................... 430 II. EXPLORING THE INTELLECTUAL PROPERTIES OF GENDER ............................. 434 A. Performative Model of Gender ........................................................... 436 B. Gender Resistance and Parodic Properties ........................................ 439 C. Unscripting Gender ............................................................................ 443 1. An extrinsic approach: Prohibiting identity scripting................ 444 2. An intrinsic approach: Scripting “based on sex.” ....................... 452 III. RESCRIPTING GENDER(S) .............................................................................. 457 A. Implications of the Morphological and Performative Models ........... 457 1. Materiality and morphology. ....................................................... 459 2. Rescripting gender expression. ................................................... 463 3. Transgender equality and sex-segregated spaces. ..................... 467 B. Toward a Model of Gender Pluralism ................................................ 474 1. Sex without scarcity. .................................................................... 478 2. Protecting gender expression ...................................................... 487 CONCLUSION ....................................................................................................... 493 INTRODUCTION There is a fundamental revolution under way regarding the relationship between gender and the state, both domestically and internationally. Across the world, the rise and visibility of transgender rights movements have forced a persistent rethink- ing of the legal presumptions associated with science, sex, and gender. For years, the law has largely maintained a steadfast commitment to the idea that one’s assigned sex—referring to the binary polarities of male and female—operated as a relatively stable fixture, capable of being mapped onto one’s gender identity 2017] The Numerus Clausus of Sex 391 and self-perception. This expectation of stability translated into a basic presumption within law and policy that gender identity and assigned sex almost always align with one another—that the binary formation of sex operated as a basic organizing prin- ciple to formalize and reify gender expression, sexuality, and so forth. In turn, antidiscrimination jurisprudence reflects these principles and, with the exception of a minority of cases, has his- torically labored under the perception that gender identity and assigned sex rarely conflict with one another. The myriad of le- gal regulations that deploy sex classifications rest on this pre- sumption; everything from the procurement of passports to ac- cess to social services to the gathering of data relies on the presumption of the binary, fixed nature of assigned sex. Today, these perceptions are increasingly confronted with the reality that the relationship between gender and sex is far more complicated than the law currently recognizes. Our global culture and legal landscape are replete with examples that con- tinually demonstrate the discontinuity of the relationship be- tween gender and sex, calling for a more complex representation of reality.1 In 2014, Facebook decided to offer its users more than fifty terms for gender self-identification, recognizing that many people use a multiplicity of terms other than male or female to describe themselves.2 As of 2017, at least three people in the United States have been able to obtain “nonbinary” or “intersex” as their legally designated gender.3 Indeed, the transgender 1 In the introduction to their pathbreaking volume published in 2006, Transgender Rights, the authors observed that more than sixty colleges and universities now include gender identity as part of their nondiscrimination policies. Paisley Currah, Richard M. Juang, and Shannon Price Minter, Introduction, in Paisley Currah, Richard M. Juang, and Shannon Price Minter, eds, Transgender Rights xiii, xiii (Minnesota 2006). Today, eleven years later, that number has grown to over 999 colleges and universities that have nondiscrimination policies that include gender identity or gender expression, in- cluding those that forbid gender discrimination. See Colleges and Universities with Non- discrimination Policies That Include Gender Identity/Expression (Campus Pride), ar- chived at http://perma.cc/BP99-2NHN. 2 See Daniel Funke, Facebook Adds New Gender Identification Options, Gender Rights Continue to Grow (Red & Black, Feb 24, 2014), archived at http://perma.cc/W7YD-588X. 3 New York City issued the first birth certificate with intersex in the gender field in December 2016 after receiving a court order from a state court. See Sam Levin, First US Person to Have “Intersex” on Birth Certificate: “There’s Power in Knowing Who You Are” (The Guardian, Jan 11, 2017), archived at http://perma.cc/3NKX-MYU8. The Cali- fornia legislature is currently considering legislation to allow the state to issue birth certificates, drivers’ licenses, and court orders specifying a “nonbinary” gender. 392 The University of Chicago Law Review [84:389 rights movement is—and has always been—global in scope; many courts, countries, and municipalities throughout the world have faced similar pushes toward pluralism, leading some na- tions to offer a third category for those who identify as some- thing other than male or female.4 Popular culture, too, has begun to reflect these identities.5 Even before Caitlyn Jenner