Any parent that signs off on their prepubescent child being put on puberty blockers and/or going through any type of "gender reassignment" procedure needs to charged with abuse... as well as the doctor that agreed to go along and administered the drugs or performed the procedures.
When the kids become legal adults, they can do as they wish... but prior to that, no.
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people