Cruz's Canadian citizenship was governed by the 1947 Citizenship Act.
Here is the Act
http://historyofrights.ca/wp-content/uploads/statutes/CN_Citizenship.pdf
Section 10 governs naturalization. Under that section Cruz's parents would have been required to reside in Canada for four years before they could apply for Canadian citizenship.
Section 10 of the 1947 Citizenship Act of Canada:
(b) Have been lawfully admitted to Canada for permanent residence therein;
(c) he has resided continuously in Canada for a period of one year immediately preceding the date of the application and, in addition, except where the applicant has served outside of Canada in the armed forces of Canada during time of war or where the applicant is the wife of and resides in Canada to a Canadian citizen, has also resided in Canada for a further period of not less than four years during the previous six years immediately preceding the date of application.
Cruz would be a natural born Canadian citizen under Part 1 Section 5 (a) of the Act:
5. A person, born after the commencement of this Act, is a natural-born Canadian citizen: -
(a) if he is born in Canada or on a Canadian ship:
There is nothing in the Act about first having to give up any other citizenship.
There is a section of the Act that discusses a child with dual citizenship being allowed to renounce their Canadian citizenship if they so choose.
Part III
Section 17. (1) Where a natural-born Canadian citizen, at his birth or during his minority, or any Canadian citizen on marriage, became or becomes under the law of any other country a national or citizen of that country, if, after attaining the full age of twenty-one years, or after the marriage, he makes, while not under disability, and still a national or citizen, a declaration renouncing his Canadian citizenship, he shall thereupon cease to be a Canadian citizen.
If Canada did not recognize dual citizenship there would be no reason for them to have Section 17.
Cruz was a natural-born Canadian citizen who "at his birth" "became" "under the law" of the United States, a "citizen of" the United States.
As a US citizen Cruz’s mother was under the jurisdiction of the United States. It doesn’t matter what Canada’s law was, they can’t take US citizenship away from your child by automatically bestowing Canadian citizenship on them. US law is all that matters here and that law bestowed US citizenship on him at birth.
If your last sentence is correct, then Ted Cruz was naturalized at birth, an act of a law; not a natural born citizen.
Being a natural born citizen means that one cannot be anything else, and no act of law affects the citizenship status. For a natural born citizen, born on the soil, AND born to parents who are both citizens, there is no question of divided allegiance, no dual citizenship, no claim of any other citizenship, no question that such child is anything other than 100% citizen of one nation; neither due to geography, nor to parentage.
If Ted were naturalized at some point (still unproven), he might be eligible for the Senate seat he currently holds.
Ted Cruz will never in this lifetime be constitutionally eligible to become president of the USA.
Citizenship is germane but not the issue. The question he must answer is — were you born in the United States. So many are way off base on this. I’m trying to help because they are so ignorant of the real issue.
I want to know if his mother had effectively renounced citizenship prior to his birth. Whether that action would preclude his obtaining citizenship at birth. His renouncing Canadian citizenship, while not legally being an American citizen would be a disaster for him.