And that's where this gets interesting. Every attempt to patch the loophole seems to require another arbitrary line.

Years of hormones? How many?
Surgery? Then identity alone isn't enough. Doctor's certification? Now a doctor determines whether your identity is legitimate. No medical requirements? Then what's the principled basis for rejecting Kanter?

At some point the simplest rule becomes the one everyone spent years insisting was unnecessarily complicated, women's professional basketball is for biological females.