> I don't see how Article III would prevent the establishment of a U.S. District Court outside the territory of the U.S.
It wouldn't, it would prevent something other than an Article III court from being established by treaty (and anything established by treaty would not be an Article III court.) Congress can establish, and has established Article III courts outside of the US (notably, the U.S. Court for China.) Not, of course, that such a court would be necessary to allow foreigners to sue US officials for violations of Constitutional rights, since offenses cognizable under US law that occur outside of any established judicial district can already be filed in district courts; see, 28 USC Sec. 1391(b)(1) and (b)(3).
(Aside from reducing inconvenience in the US government policing US citizens when granted an extraterritorial privilege to do so, as was the case with the sui generis US Court for China, the main benefit of a foreign-located US Court would be to provide a US -- from a legal perspective -- venue for parties to sue non-US persons local to the area where the court was located where forum non conveniens is less likely to be invoked as a reason for dismissal.)
> A treaty cannot establish such a court
But, upthread, you suggested that a court for the purpose you had in mind would be established by treaty, which I took issue with precisely because a treaty cannot establish such a court.
That's splitting hairs, in my opinion. There is a distinction possible between "established by treaty" and "established by an Act of Congress pursuant to a treaty", but I didn't think it was necessary to make it upthread.
My main point was that foreign states need not become one of the United States to be protected by certain rights clauses in the U.S. Constitution. The key question is how to make the agents of the U.S. obey U.S. laws when outside of U.S. territorial jurisdiction, and there are many possible answers that do not involve extending U.S. territorial jurisdiction beyond its current bounds.
If there are no district courts outside U.S. territory, suing the U.S. as a foreign person may become prohibitively expensive in relation to the magnitude of the offense. The suit could further be impeded by using immigration laws against the plaintiff, possibly impeding discovery or appearances. Retaining a local attorney would be de facto required rather than optional, and hourly rates might combine with currency exchange rates and national economies to ensure that the price tag is simply too high.
> My main point was that foreign states need not become one of the United States to be protected by certain rights clauses in the U.S. Constitution.
But the courts argument is irrelevant to that. To the extent that the US Constitutional rights (or other rights under US law) extend to foreign nationals in foreign territory, the existence of a US court on their soil is irrelevant to such protection, it has no effect either way. So the whole court thing was a non sequitur.
> If there are no district courts outside U.S. territory, suing the U.S. as a foreign person may become prohibitively expensive in relation to the magnitude of the offense.
That might be a practical concern, but it is irrelevant to the actual legal concern, which is that it is well-established law that many protections of the US Constitution do not, in fact, apply to foreign persons outside of the US in the same way as they apply either to US citizens or to persons within the US (some don't apply at all, and even for those that do, the differences in factual circumstance between US and foreign jurisdiction and the fact that the US government has express granted powers in governing relations with foreign nations changes how they apply), and that, in fact, to be protected by those rights in the same way as would be the case for those within the US, the states they were in would, contrary to your argument, need to become part of the United States.
It wouldn't, it would prevent something other than an Article III court from being established by treaty (and anything established by treaty would not be an Article III court.) Congress can establish, and has established Article III courts outside of the US (notably, the U.S. Court for China.) Not, of course, that such a court would be necessary to allow foreigners to sue US officials for violations of Constitutional rights, since offenses cognizable under US law that occur outside of any established judicial district can already be filed in district courts; see, 28 USC Sec. 1391(b)(1) and (b)(3).
(Aside from reducing inconvenience in the US government policing US citizens when granted an extraterritorial privilege to do so, as was the case with the sui generis US Court for China, the main benefit of a foreign-located US Court would be to provide a US -- from a legal perspective -- venue for parties to sue non-US persons local to the area where the court was located where forum non conveniens is less likely to be invoked as a reason for dismissal.)
> A treaty cannot establish such a court
But, upthread, you suggested that a court for the purpose you had in mind would be established by treaty, which I took issue with precisely because a treaty cannot establish such a court.