Fourth Amendment issues aside, as a non-American this strikes me as an obvious violation of Human Rights (especially the right to bodily integrity in particular).
I'm not sure what the situation is like in the US, but I'm fairly certain that in my country you couldn't be subjected to an x-ray scan without consent, unless there is sufficiently strong suspicion and an x-ray scan would be the least invasive option (e.g. this is why you can be forced to give a blood sample if you refuse to take a breathalyser test when assumed to DUI).
I have no idea how random drive-by x-rays on the street could be considered reasonable and not in violation of Human Rights unless you're in a freakin warzone.
I'm not sure what the situation is like in the US, but I'm fairly certain that in my country you couldn't be subjected to an x-ray scan without consent, unless there is sufficiently strong suspicion and an x-ray scan would be the least invasive option (e.g. this is why you can be forced to give a blood sample if you refuse to take a breathalyser test when assumed to DUI).
I have no idea how random drive-by x-rays on the street could be considered reasonable and not in violation of Human Rights unless you're in a freakin warzone.