In most jurisdictions in the U.S., a birth certificate’s sex marker as decided by the appearance of the infant’s genitals creates a rebuttable presumption of legal sex requiring specified (but widely varying) evidence to overcome. These requirements for recognition are generally illogical, inconsistent, and unattainable for most trans* people. As a result, the majority of trans* people in the U.S. end up with conflicting sex markers on their identity documents. This regime of a legal sex designated at birth directly harms the most vulnerable and unfairly distributes life chances. The current U.S. rules governing marriage-based immigration for trans* people provide a valuable case study of the inadequacy of the predominant approach to sex classification in the U.S. Within the context of the many other harms that trans* people (and queer cisgender people) experience partly as a result of legal sex categorization and regulation, the many problems of the U.S. rules governing marriage-based immigration for trans* people demonstrate that the only solution to the current mess is the total elimination of “sex” as a legal category.