Note that the "border" here is not the coastline, but the limits of territorial waters (12 miles). This also means that proximity to, say, the upper Chesapeake Bay or the southern tip of Lake Michigan aren't relevant, as those coastlines are of internal waters and not the larger ocean.
> Note that the "border" here is not the coastline, but the limits of territorial waters (12 miles)
No, the Border Patrol interpretation of the “reasonable distance from the external boundary rule” is that it extends to at least 100 miles from any land border or any part of the US coastline (whether or not it is or is in proximity to an international border.)
That's what the ACLU says the Border Patrol's interpretation is. When I actually read the regulations and the statutes themselves, as far as I could infer, the external boundary was meant to refer to the international water boundary.
I'm afraid I don't recall the exact citation off the top of my head, but I'd like to see more evidence for the ACLU's claims than, well, just the ACLU saying so. Especially when the ACLU itself points out that the law and regulations doesn't actually give the Border Patrol some of the powers it has.
(I should note there's a distinction between the actual legal authority and the actual policies applied in practice--I'm arguing that the legal authority is 100 miles from the international waters boundary; that the Border Patrol is exceeding that is probable, but the ACLU is, IMO, conflating the legal and actual effects to lobby specifically against the law rather than lobbying against the Border Patrol acting illegally).