There is a fascinating piece in the New Yorker about transgender rights and the way the legal fights are progressing.
The most interesting bit to me is that the question of immutability will come up, inevitably. The notion that gender is/is not a choice, the way it did in the gay rights movement. One of the elements that strengthened the case for gay rights was that it wasn’t a choice. As the article points out, by implication, this states that if it was a choice there might be grounds for such discrimination.
Identity is a much different beast, something that is to be discovered and expressed and understood. It manifests in different ways over time. Declaring it immutable is going to be much more difficult.