[thatcat]

Yes, either we are in US territory and US has authority to apply it's laws under the restrictions of its constitution or we aren't and they have no particular authority to search at all with some exceptions from military/coast guard.

[wfunction]

Hmm... I wouldn't say they have no authority to search you there -- only that it is abusive for them to do it without good reason, or to refuse to verify your identity first if they can do so. (Extreme example, but if they had good reason to think you might have explosives on you, I would sure as hell want them to search you even before you've had a chance to talk to the CBP officers.)

I haven't though this through, so I don't know what the implications are, but I think it makes sense to say there are multiple "borders" that we need to think about here -- an "outside" border, which other countries recognize as the border of your territory & jurisdiction, and an "inside" border, which is the one you cross by showing your passport. In between these two borders -- assuming (crucially) that you're crossing these borders out of your own volition -- I would say that the country has every authority to do more or less anything it feels like: you're in its territory, and they have no reason to believe you belong there (effectively, you're a trespasser). At that point, the best you can hope for is that you're entering a sane country that does something humane. If you're not, then either you're a citizen and should have been advocating to change the system before leaving, or you're not a citizen, in which case it's other people's country and they get to run their country however they like (sorry).

Again, I haven't thought through all the implications, so there might be some glaring problems... but this is what my brain right now thinks would be logical. None of these would apply if you're being forced to cross borders (war, persecution, refugee, etc.); I don't really know what to do in that case. But those are rare enough that you can't expect the country to treat every single traveler as a potentially persecuted refugee.

[thatcat]

If you let the gov create an extrajudicial zone where they aren't subject to their own laws that becomes a very attractive option. I agree that if there is resonable suspicion, that falls within the pre agreed upon laws. Ideally, to prevent hypocracy and gradual constitutional errosion via offshoring, the fundamental rules applied internally should also apply externally.