If I met you on the street and asked you what gender I was, you'd look at me funny and say, "Duh, you're female." I'd agree, because I'm what certain people call cisgender. Which means that I feel—I have always felt—that my identity is accurately reflected by the gender assigned to me at birth. Cisgender is the opposite of transgender.

It's a useful word in the sex-positive community, where people work to be sensitive about transgender issues. Even so, language about gender is still politically perilous. This Saturday, sex educator Midori is throwing a sex/play party called "Bang 4 the Buck." It's a charity event for the AIDS/LifeCycle program. This is the sixth annual Bang, and it's always a popular affair. However, if you're a man, there will be no Banging for you: It's a women-only party.

What's the perilous part? Deciding who can attend. What makes someone a woman? How can I determine your gender just by looking at you? To put it bluntly, when you throw a women-only sex party, how can you be trans-friendly while protecting attendees from the inevitable cisgender man who wants in?

This isn't a new dilemma. Historically, the lesbian community hasn't always been welcoming to transgender women. Women's sex parties I attended in the 1990s discouraged anyone but cisgender women by stating "women-born women only." A creative phrase coined by the Seattle leather-dyke community was the "dick-in-a-drawer rule": You must be able to slam your dick in a drawer and walk away to attend women-only events. As one dyke expressed it: "No way is some guy just gonna put on a dress and say, 'Oh, I'm a woman now.'"

That's the community where my sex activism began, but things have changed. I think cisgender women—including me—have gained a broader understanding of transgender women. I don't support attendance polices based on genital configuration, and I'm not alone. In an attempt to compromise, some organizers say that anyone with an F (for female) on their ID can attend.

But while that works for transwomen who've legally changed genders, opponents say it excludes people who self-identify as female but choose not to change their ID. Due to ambiguous phrasing, members of the trans community mistakenly thought Midori was enforcing the "F on your ID" rule for the Bang party, and protests were made online. Midori's official stance: "Anyone who is female-identified is welcome at Bang 4 the Buck. An F on your identification is not necessary—we understand the obstacles around this."

I asked gender activist Kate Bornstein her opinion of women-only parties. She replied: "How to handle opportunistic cisgender men? I haven't got a clue. But there's nothing morally or ethically wrong with being gender exclusionary for the purpose of self-perceived safety. It all boils down to 'don't be mean.'" recommended