According to the Canadian Citizenship Act of 1946, also referred to as the "Act of 1947" because of its effective date, Canada did not allow dual citizenship. This was the first citizenship act in Canada to create a new citizenship status separate from being considered British Subjects. With the pride of a nation first enacting the right to become Canadian Citizens, it would stand to reason why they also chose at the time to not allow dual citizenship. According to the Government of Canada's website, the heading "History of citizenship legislation" states the following:
Up to January 1, 1947, there was no legal status of Canadian citizens, only British subjects. This Act gave legal recognition to the terms “Canadian citizen” and “Canadian citizenship”. The Act established who was and who could become a Canadian citizen. There were many provisions for loss of citizenship, including retention provisions for the first and subsequent generations born outside Canada. The Act also contained provisions which provided special treatment for British subjects. In general, Canadian citizens who acquired citizenship of another country automatically lost Canadian citizenship (dual citizenship was not recognized).
It was not until the passage of the "Citizenship Act" effective on February 15, 1977 that the ability to hold dual citizenship was changed.
The Citizenship Act, effective February 15, 1977, replaced the 1947 Act with a more equitable statute. For example, British subjects no longer received special treatment and dual citizenship became recognized. There was only one provision for automatic loss of citizenship, limited to persons born in the second or subsequent generation outside Canada unless they took steps to retain their citizenship by their 28th birthday.
In the following years, Canada has continued to go in the direction of granting increasingly more generous grounds for automatic Canadian citizenship, seemingly in an attempt to continue the strengthening of Canadian nationalism. To learn more about the beginning growth of Canadian nationalism, read in the Government of Canada archive, "Forging Our Legacy: Canadian Citizenship and Immigration, 1900-1977".
In order for Ted Cruz to have "become" a US citizen at birth in 1970, his mother would have had to retain exclusive citizenship to the US and filed a CRBA (Consular Report of Birth Abroad) to "obtain" exclusive US citizenship at the time for her son Ted and renounced his automatic "naturally acquired" Canadian citizenship. The process in itself is considered a very abbreviated form of "naturalization", thereby making such persons born outside of the OFFICIAL territories of the United States absolutely ineligible to become President of these United States in at least this one circumstance alone. Given that Canadian law did not allow dual citizenship at the time, then IF his mother filed a CRBA in 1970, his Canadian citizenship would likely have needed to be renounced before a new US citizenship could be granted.
Ted's Father has publicly admitted he became a Canadian citizen in 1968. If his mother's first husband with surname of "Wilson" was also a Canadian citizen (unconfirmed), she would have become a citizen before his father. Even if her first husband was not Canadian, according to Canadian law, she would still have automatically become a Canadian citizen in 1969 after having a Canadian spouse (Ted's Father) and residing in Canada for 1 year. This information substantiates the reports claiming that both of his parents appeared on the Canadian voter's rolls. There is now an unconfirmed claim that someone has supposedly verified that they indeed both voted in the October of 1972 federal Canadian election.
If both of Ted's parents became exclusive citizens of Canada by 1969, then even if his mother tried to file a CRBA, she would not have been able to confer US citizenship to her son as she was no longer a US citizen herself. Even if she somehow retained US citizenship, Ted could not have been granted dual citizenship as it was against Canadian law. The only thing that is certain is that Ted Cruz automatically became a Canadian citizen the instant he was born on Canadian soil and that fact is absolutely irrefutable. Likewise, the release of his mother's birth certificate certainly settles absolutely nothing.
Ted Cruz did not renounce his Canadian citizenship until 2014. All FOIA requests have been denied requesting a copy of a CRBA and he has not released it or any other naturalization papers. There is currently no proof available to show he ever became a US citizen. It is perfectly understandable that he would not want to release any such naturalization documents as one cannot be considered both "naturalized" and :"natural-born". Senator Cruz has repeatedly claimed that he did not have to go through any type of naturalization process (including a CRBA), that he was automatically a US citizen by birth but that does not match US law for persons born in another country. If indeed that was just assumed and nothing was ever filed to correct that erroneous assumption, then he never has become a US citizen and referring to a previous article, Ted Cruz must show naturalization papers to keep his US senate seat.
Even though Marco Rubio also can't be a natural-born citizen and is instead considered an "anchor baby", his parents did become US citizens 4 years after his birth. He is therefore legally able to serve in the US Senate regardless of your interpretation of birthright citizenship.
Contrary to recent blatantly false headlines, there have been at least now 5 lawsuits filed in 5 different states challenging Ted Cruz' eligibility to become President, a majority of these also equally challenge Marco Rubio's eligibility even though it is rarely reported. The states are/were: NH, VT, FL, IL and TX. Every Republican candidate running for President should be immediately filing lawsuits to have both Ted Cruz and Marco Rubio removed from the presidential contest as their continued participation presents an unlawful detriment to everyone else's candidacy.