I have a friend in Israel who has been denied work and the job was given to a man with the reason "He needs to support his family." At the time this woman’s husband was unemployed and the family was literally starving to death. At other times other women I have known were told they were "too attractive" and would make the men they would be working with uncomfortable, even though the women upheld the strongest standards of Tznius. Does halacha have any laws against gender discrimination in employment?
I am unaware of Halacha referring to discrimination in hiring. Obviously, the Mitzvot of Tzedakah and Chesed would apply to hiring, but these can rarely be enforced by Beit Din. OTOH, the Halacha recognizes that common law and current practice are binding in matters of the marketplace. I would advise anyone who has suffered such discrimination to check with the legal council for workers of the Histadrut (in Israel) and if there is a clear ruling I would not be surprised if a Beit Din would offer relief.