Can you please provide a link, xzins???
Yes, Canada restricted dual citizenship between 1947-1977, and loss of citizenship happened for those naturalized in another country. Cruz Sr became a Canadian citizen prior to Ted Cruz’s birth. His mother did not.
See: http://dictionary.sensagent.com/canadian%20citizenship%20act%201946/en-en/
FWIW, the above also argues that under the law CURRENT at the time of Ted Cruz’s birth, his mother’s filling out the paperwork on Ted should have caused him to lose his Canadian citizenship.