If I give that argument the benefit of the doubt, I'm left trying to figure out why it bothers me to have CBP look through my phone but not through my luggage.

If I give that argument the benefit of the doubt, I'm left trying to figure out why it bothers me to have CBP look through my phone but not through my luggage. I think the issue is what sort of contraband or dutiable good might I have on my phone in particular? I don't understand what I could possibly be bringing into the US, especially as a citizen, on an electronic device that wouldn't fall under the scope of a required warrant. If I have an invasive species, for example, it seems reasonable to search for that because of the imminent threat of bringing it into the country. But I don't understand what could be on my phone that would justify that kind of search in the absence of a warrant or probable cause with regard to my situation in particular. I don't agree with the argument that borders are "twilight zones" of territory, because if they were, you'd end up in this kind of Zeno's paradox situation, and I think as a practical test, you could ask how the US would feel if foreign powers just sort of claimed the right to occupy border search zones. There probably is some grey area, but once you get to the search space, it's not grey anymore as the CBP is asserting their authority over it. I think the idea that the border zone includes 100 miles around border points speaks to the absurdity of the idea that the border is some kind of twilight zone where constitutional protections don't apply. This is one of these decisions that seems to me to fly in the face of common sense and reflects some subjective feeling on the part of the judge that having CBP look through your phone "seems reasonable to them," which to me isn't reasonable at all.