It just took a lawsuit.
I'll leave you with this quote:
The problem with a narrow definition, said Christopher Stoll of the National Center for Lesbian Rights, which represents the plaintiffs, is how to define “gay.”
“How do you prove if someone is gay or straight?” he said. “One of the most disturbing things about the league’s position in this case is that there’s only one way of being gay, or one view of being gay. The definition did not include bisexual, or transgendered. Our clients break the stereotypes of what gay is supposed to be.”