"at" is NOT "in." You have to step across a threshold opening to be "in" something. I don't cum at my wife, I cum IN her. I don't go "at" my home, I go "IN" my home. I don't arrive "at" the U.S., I arrive "IN" the U.S. This has been argued before. Ports of entry at either border have a "grey zone" where the actual entry point is, whether it's a building or a gate, that has to be crossed before someone is considered inside U.S. property. A person can be turned around inside that grey zone, or even held inside that zone if the country they're leaving refuses entry, too. That was one of the issues of the crisis at the Southern Border. But since they hadn't successfully crossed IN to the U.S., they were considered still IN Mexico by the U.S. Govt. The border zone at the officially recognized entry points is, in some cases, almost 100 yrs wide. A person transiting that area is still considered to be AT the border, since a borderline is a threshold object, not a building, domicile, etc. A country is considered to be a domicile for a whole population of people. That's why we have phrases like home-land.

It seems to me that neither side of the argument successfully presented their case in this, but we'll see. It's clear which way most of SC(r)OTUS will vote, though. The question is, which of them will side with the Dems?