This chapter describes the changes in legal understandings of sex and gender themselves. It explains the impact, and limitations, of significant changes within the law. The chapter examines the general movement in the law towards greater formal gender equality and gender neutrality. It focuses upon the question of how to balance the autonomy of both parties, recognising the sensitivity of the issues involved. The chapter discusses that trans covers a broad spectrum of gender identities, but the extent to which the law recognises and accommodates the varies. It shows that legal attempts to protect trans people from discrimination may not encompass intersex people. The chapter shows that the specific legal issues faced by intersex people, which begin at birth when English law requires that intersex babies are registered as either male or female. It explains the existing system of gender assignment itself. The chapter discusses how the law regulates gender, and how gender influences the application of the law.