Ancestor Naturalized as American? You May Still Be Canadian

If your Canadian ancestor became a US citizen between January 1, 1947 and February 15, 1977, they automatically lost their Canadian citizenship on the day they took their oath of allegiance to the United States. No court order, no notification, no grace period. The Canadian Citizenship Act of 1946 made the loss instantaneous.

At least 240,000 Canadians naturalized as Americans during that thirty-year window. Two pieces of legislation undid that loss: Bill C-37 in 2009 and Bill C-3 in 2025. Together they retroactively restored citizenship to those individuals and opened the path for their descendants.

Canada's first dedicated citizenship law came into force on January 1, 1947. It created a distinct Canadian citizenship for the first time, but also included a hard provision: any Canadian who voluntarily acquired the citizenship of another country ceased to be Canadian on that date, instantly.

Becoming a US citizen ended Canadian citizenship the day the foreign oath was taken, whether the person fully understood the consequence or not.

This stayed the law until February 15, 1977, when Canada's current Citizenship Act allowed dual citizenship going forward. The 1977 law was not retroactive. Canadians who had naturalized as Americans before that date remained stripped.

Before 1947, Canada operated under British subject law rather than distinct Canadian citizenship. A Canadian woman who married a foreign national (including an American) before January 1, 1947 lost her British subject status automatically under the rule that a woman's nationality followed her husband's.

The 1947 Act stopped this practice going forward but did not automatically restore status to women who had already lost it. Those women had to apply to be naturalized as if they were newcomers, even though they were born Canadian.

Bill C-37 came into force on April 17, 2009, retroactively restoring Canadian citizenship to most Lost Canadians, including:

• Canadians who naturalized in another country between January 1, 1947 and February 14, 1977
• Canadians who lost citizenship under the old patrilineal rules, where citizenship passed only through fathers
• People who lost citizenship as children when a parent naturalized abroad

The restoration operates as if those individuals had remained Canadian throughout. Someone who naturalized as American in 1959 is now legally treated as having been Canadian the entire time, retroactive to birth.

One limitation Bill C-37 left in place: it did not help second-generation Canadians born abroad after February 15, 1977. If your parent was retroactively restored as Canadian but you were born in the US in 1983, your citizenship was recognized. Your own children, however, were still blocked by the first-generation-born-abroad limit.

Bill C-3, effective December 15, 2025, removed the first-generation limit for anyone born before that date. This is what makes the 1947-1977 history directly relevant to people applying today.

Here is how it plays out. Miriam's grandfather Harold was born in Winnipeg in 1921. He naturalized as an American in 1954. Under the 1947 Act, he lost Canadian citizenship that day. Harold's daughter Janet was born in Minneapolis in 1957, at a time when her father was not legally Canadian. She was not Canadian at birth either.

Under Bill C-37, Harold's citizenship was retroactively restored. Janet became recognized as a first-generation-born-abroad Canadian. Under the old rules, Miriam (born in 1982) was second-generation and past the limit. Under Bill C-3, that limit no longer exists. Miriam applies with a CIT 0001, documents the full chain, and receives her certificate.

Documentation follows the same structure as any citizenship-by-descent application, with one useful addition.

Standard documents: long-form birth certificates for every person in the chain, naming both parents, plus marriage certificates for any name changes between generations. For what qualifies as an acceptable certified copy, see the certified copy guide.

Useful addition: If the ancestor naturalized as American during 1947-1977, include their US Certificate of Naturalization (Form N-550 or N-570) if you have it. You do not need to prove the loss of citizenship separately. IRCC knows the statutory history. The naturalization certificate simply helps the officer trace the chain accurately.

If the papers are not in the family's possession, the US National Archives holds records for naturalizations from 1790 onward. Naturalizations before September 27, 1906 are held by local courts; records after that date are with US Citizenship and Immigration Services (USCIS).

On the CIT 0001 form, select "Born outside Canada to a Canadian parent (citizenship by descent)" in Section 2. This is correct even when the chain runs through an ancestor whose citizenship was retroactively restored under C-37. Include a brief cover letter noting the naturalization history so the officer does not have to infer it from the documents alone.

If your family chain includes someone who naturalized as American in the 1947-1977 window, the legal work is behind you. Bills C-37 and C-3 already fixed the statute. What you need now is the certified birth certificates and marriage certificates that prove the unbroken line from your Canadian-born ancestor to you. MaplePass maps the complete chain and identifies exactly which documents to order for each link.