Dr. Guy:
That phrase has nothing to do with "being lawful", but was put in there to include the parts of the country (at the time) that were not states, but territories of the states (Ohio being one as it was a part of Virginia).
Thus that is of no help. The phrase was being used to declare that residents of Ohio were citizens by virtue of being ruled by Virginia law.
That would make sense, and probably is part of it, but to see the full meaning you have to look back to who wasn't "subject to the jurisdiction thereof".
Indians weren't, they were "subject to the jurisdiction" of their tribes.
Slaves weren't, they were "subject to the jurisdiction" of their owners.
Endentured servants weren't, they were "subject to the jurisdiction" of their "sponsors" until their debt was worked off.
Those who fell behind in their debts weren't, they were "subject to the jurisdiction" of those they owed money too.
With few exceptions, women weren't, they were subject to the jurisdiction of their fathers and husbands.
On the other hand, diplomats, soldiers, and other government sponsored travellers were "subject to the jurisdiction" in any nation that recognized the U.S.
It did matter where you lived, but what mattered even more is that you were a free person. Those who weren't had few "rights" other than what was granted them by those whose jurisdiction they were subject to.