Neither the Equal Protection Clause of the Constitution, its state constitution counterparts, nor any federal antidiscrimination laws like Title IX or Title VII expressly cover discrimination on the basis of sexual orientation. But some courts have construed existing protection against sex discrimination to apply when the plaintiff suffered discrimination for her or his failure to conform to gender stereotypes. However, courts have not held that being gay or lesbian per se is a failure to conform to gender stereotype and actionable as sex discrimination. Thus, the gender stereotype theory of sex discrimination is only potentially available so some (perceived) gay plaintiffs -- those who faced discrimination regarding their appearance or behavior, rather than on the solely who they date, are attracted to, and sleep with (or are believed to sleep with).
Osborne also believes that the gender stereotype theory of sex discrimination is particularly incompatible with discrimination claims that arise in the context of athletics, as she explains:
Female athletes are caught in a socio-cultural contradiction--to be an athlete is to be masculine, automatically calling the athlete's femininity into question. When a woman's femininity is challenged, her sexuality is questioned as well. In essence, being a female athlete itself is a failure to conform to accepted gender stereotypes.Owing to these difficulties and uncertainties arising from the gender stereotype theory, Osborne argues that universities should adopt policies specifically protection against discrimination on the basis of sexual orientation.