[hardoncollider]

Uh, the gender the person identifies with. That's all.

[knicholes]

Then I hardly see how this law changes anything. Can't one identify one's gender fluidly, sometimes including both at times?

[MagnumOpus]

No, legally one can't. One can change their legal gender, but one has to decide.

[knicholes]

Ah, of course. Thank you for helping me realize what should have been painfully obvious. (but seriously, though, thank you)