Circular. The very first law that applies to illegals is that they don't belong here.
You said that if illegals are not subject to the jurisdiction then:
...that would lead to a hell of a lot of prison doors being thrown open.
Yet you also said that:
A government is assumed to have jurisdiction over its territory and the people in it -- that is what makes it a government. Diplomats and Indians were exempted from that jurisdiction by specific laws and treaties.
And yet we know Indians who were not subject to the jurisdiction could be and were arrested, tried and convicted for crimes committed in the states.
So far all I get is that because they can be jailed for crimes that makes them subject to the jurisdiction. That really excludes no one and makes the phrase meaningless.
I really see no differnce between illegals and those Indians.
The Indians were outside US law while on Indian lands. The reservations were legally independent countries — their citizens were not US citizens, though the reservations were legally inside the United States. While on the reservations, they were not subject to the jurisdiction of the United States. Babies born on the reservation were not United States citizens at birth. When they left the reservations, they were subject to US (and the appropriate state) jurisdiction.
Similarly, Mexican citizens are not subject ot US jurisdiction while in Mexico. They are subject to US jurisdiction while in the US.