To me this is where gender testing, testosterone levels, etc should come into play. If you were born a male and transitioned to being female, your genetic and hormonal makeup should have to be consistent with those of a woman before competing against in an athletic event. That just ensures fairness to the competitors who were born as women and verifies the accuracy of your claim to your gender. Remember you're no longer pushing some fluid concept of gender, now you're entering a world with a practical reason for having a binary concept of gender and competing within that world, which also goes to great length to level its playing field.

That said, and this may draw ire from some, I absolutely do not think that such standards should be applied to women who were born women, as we are seeing presently with Caster Semenya and as we may see with other female athletes born with some male traits/hormonal levels. To me that seems vastly unfair because it relegates them to an interstitial position where they basically cannot compete in their sport. Furthermore their genetic reality is not of their doing in any way, shape or form. We couldn't say that LeBron James has more testosterone than John Stockton, so now LeBron has to play in some other league or Stockton has to go to the WNBA. It just seems crazy to me that someone born a woman could be subjected to that level of scrutiny and humiliation. It doesn't seem pleasant or totally fair that a transgender person would be, but it seems like a necessary safeguard to protect the fairness and equitable division of competition.