The federal Fair Housing Act prohibits discrimination in all stages of the home buying process on the basis of race, color, national origin, religion, sex, familial status, or disability. In particular, housing advertising that indicates a discriminatory preference based on one of these factors is illegal. The U.S. Department of Housing and Urban Development (“HUD”) has published guidelines for those who advertise homes for sale. You can report housing discrimination to HUD in a number of ways, including via phone at 1-800-669-7777. HUD provides a number of resources for consumers and professionals relating to fair housing. This is a good place to start: HUD.gov
State governments and many local governments have similar laws prohibiting discrimination in housing. This excellent resource can help you find local fair housing enforcement agencies around the country: National Fair Housing Advocate Online.