See ESC right:

Working conditions, just and favourable

Relevant ICESCR Articles:

02(2): The States Parties to the present Covenant undertake to guarantee that the rights enunciated in the present Covenant will be exercised without discrimination of any kind as to race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status.

06(1): The States Parties to the present Covenant recognize the right to work, which includes the right of everyone to the opportunity to gain his living by work which he freely chooses or accepts, and will take appropriate steps to safeguard this right.

Related Documents:

Convention on the Elimination of All Forms of Discrimination Against Women

Discrimination (Employment and Occupation) Convention

International Convention on the Elimination of All Forms of Racial Discrimination