The authority is the US Constitution. The US Courts are bound to interpret and uphold the Constitution when questions like this arise. That is why they exist - to settle such disputes.
Well, I took an oath to God to support and defend the Constitution of the United States against all enemies, foreign and domestic, and to bear true faith and allegiance to the same. Does that count?
My prognosis at one point in time in Iraq, where I was deployed more than once as a US Marine, was amputation of my left leg, and a double orchiectomy. They changed the plan while I was unconscious, and saved the leg and one testicle. I can still have kids, Everything functions fine, with some pain in the leg at all times. That was a happy moment waking up, and looking down expecting a stump, but finding a leg and genitalia still attached. I am quite grateful for that, and always will be.
I work for the US Navy as a commissioned officer at the largest US medical facility outside of the United States, run by the US Army and the DoD. The US government (you the taxpayer) paid for me to go to some very expensive schools, including medical school. I am grateful for that too.
Last time I checked, my US passport was still valid. So was my military passport. I think I do appreciate and understand the US Constitution tolerably well.