Can my Past Employer Refuse to Refer Me for Employment?

My employer would not give me a reference for a new position. He always had a hard time with me and all women who worked under him. Is it legal for him to refuse to refer me to another employer or to bad-mouth me when the new employer calls for a reference?

By Deskin Law Firm
It may be illegal for your past employer to refuse to refer you for employment or to say things that are not true about you if he is doing so because you are a woman. Discrimination is prohibited against protected classes of people based on your race, color, sex, religion, or national origin.

What Other Factors Should I Consider to Determine if I am Being Unlawfully Discriminated Against?