The Right to non-discrimination on grounds of sex and gender is explained in these documents:

Legally Obligating Documents
African (Banjul) Charter on Human and People's Rights (2, 3, 18(2))
Convention on Elimination of All Forms of Discrimination Against Women (1, 2, 3, 4, 5)
Convention on the Rights of the Child (2(1))
International Covenant Economic, Social and Cultural Rights (2(2), 3)
International Covenant on Civil and Political Rights (2(1), 3)