The reason I singled out the train as a particular case is that it's clearly domestic travel, not international. If there are foreigners on board, they'd have to come through some other border crossing before getting on the train. You can't get to Penn Station from outside the country without going through customs somewhere else, most likely an airport. Which means that this is not equivalent to a border crossing, unless you adopt a meaning of those terms so vague that anything within 100 miles of the border is the functional equivalent of a border crossing, which seems to be what the border patrol is doing.
And yes, it is possible to find places in the country, even in the 100-mile zone, where DHS is not engaged in abusive activity. That's cold comfort to folks who have to deal with them when they are.
ETA: if you're wondering about international train travel, like from Canada, I've taken one of those trains, from Montreal to New York. (Very scenic route, right down the shore of Lake Champlain.) The border-crossing inspection happened in Vermont, outside St. Albans, within minutes of where the train crossed the border. That's what "functionally equivalent to a border crossing" means, if it means anything at all.
I cited the examples of Georgia and Virginia to emphasize that known cases of these Border Patrol operations seem to cluster in areas that are frequently points of disembarkation for international travel.
I don't disagree with you that DHS operations are often abusive, and I have even suggested that the examples cited by that article might not be justified as "functionally equivalent". I do think, however, that the idea of a "Constitution-free zone" isn't a useful concept for describing DHS practices.
And yes, it is possible to find places in the country, even in the 100-mile zone, where DHS is not engaged in abusive activity. That's cold comfort to folks who have to deal with them when they are.
ETA: if you're wondering about international train travel, like from Canada, I've taken one of those trains, from Montreal to New York. (Very scenic route, right down the shore of Lake Champlain.) The border-crossing inspection happened in Vermont, outside St. Albans, within minutes of where the train crossed the border. That's what "functionally equivalent to a border crossing" means, if it means anything at all.