Some of the bill of rights is that, and some clearly refers to things protecting "the people". I am no constitutional scholar, but this does seem to indicate that those specific rights are rights that are intended to apply to citizens of the US.
My understanding as well; noncitizens on US soil are protected by the Fourth Amendment; outside of actual border crossings, the USG cannot search them without a warrant or probable cause.
AFAIK "outside fo actual border crossings" also extends 100 miles into the US (including the coastlines). This covers the vast majority of people in the US. I've heard stories of people being searched and harassed by police because they happened to have a foreign visitor with them:
Federal law and executive order define a U.S. Person as:
a citizen of the United States;
an alien lawfully admitted for permanent residence;
an unincorporated association with a substantial number
of members who are citizens of the U.S. or are
aliens lawfully admitted for permanent residence; or
a corporation that is incorporated in the U.S.
I doubt that "permanent residence" includes H1-b workers, or other work visas, and I very strongly doubt that it includes people on business or pleasure trips.
The NSA's language seems to derive very closely from FISA (the law itself, title 50 chapter 36),
..which in 1801 (i) has similar language, though it clarifies that the definition of "lawfully admitted for permanent residence" should be taken from "section 1101(a)(20) of title 8"
(20) The term “lawfully admitted for permanent residence” means the status of having been lawfully accorded the privilege of residing permanently in the United States as an immigrant in accordance with the immigration laws, such status not having changed.
I don't feel enlightened.
The EFF, in a surprising turn, claims that any legal resident is a US Person... normally I expect the EFF to (a) do their research correctly, and then (b) point out the worst-case scenario. This appears to be neither. https://ssd.eff.org/foreign/fisa
