This is the oath you take when joining the US Army:

I, _____, do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; and that I will obey the orders of the President of the United States and the orders of the officers appointed over me, according to regulations and the Uniform Code of Military Justice. So help me God.

The important part there is the mention of the UCMJ, which states that orders cannot be illegal, violate the Constitution, violate international law, etc.

This is exactly the first thing that popped into my mind when I heard what happened. I still clearly recall the WPRI news video of the fire mentioned in the Wikipedia article. That news crew had just shown up to report on the band that was playing, and they got clear footage of the nightmare. You could see bodies stacked up at the door as hundreds of people pushed to get out of the inferno… You can probably still find the video on smaller video sharing sites if you dare to go looking for it.

Biometrics are not usernames. They are physical identifiers and unlike usernames you can’t change them.

I used to work in a datacenter that required you to go through a mantrap to access. It required three things:

1. Something you have (a card key)
2. Something you know (a PIN)
3. Something you are (biometrics)

To get to the datacenter floor you use a card key to open the door to the mantrap. It’s a small vestibule about the size of a phone booth. Once inside the door closes. You then enter your PIN on a keypad and place your hand on a biometric scanner. Once your hand is recognized the inner door opens and lets you into the datacenter. I was told the mantrap also weighed you and compared that with previous trips through to make sure somebody else didn’t sneak through with you.