Carter gave it back to them so I guess so. Not sure exactly what type of “ownership” we had.
At the time of McCain’s birth, was the Panama Canal Zone U.S. soil?
What the Senate did, defacto, was affirm that they believed to be natural born one had to have citizen parents and be born on U.S. soil, by Leahy's own words in the Sense of the Senate resolution!
Before the hearings there was no question of two American citizen parents for McCain yet they held hearings and issued a resoultion. If natural born meant to them one or the other, they would not have held hearings!
Since Leahy leads his resolution with 'whereas' two parents, we know they were just focused upon the place of birth already having settle the issue of parentage. So, at least in terms of what the Seante did, soil and parentage are both vital to the issue of natural born citizenship, not just 'where born'.