Many people in Brazil find out that their grandfather became a naturalized Brazilian and stop there. They assume the grandchild path to Portuguese citizenship is closed. In most cases, that conclusion is wrong. Portuguese law has a mechanism that gave the nationality back to people who lost it by voluntarily naturalizing abroad.
The answer depends on one detail in the grandfather's birth record in Portugal: is there an annotation recording loss of nationality? If there is not, the grandfather is probably still considered Portuguese by origin today. And paragraph (d) of article 1(1) of the Nationality Law stays open for the grandchild.
When naturalizing caused loss
Portuguese law before 1981 said that voluntarily acquiring another nationality caused the automatic loss of Portuguese nationality. A grandfather who emigrated in the 1950s or 1960s and became a naturalized Brazilian formally lost his nationality of origin at that moment. It was called loss by operation of law.
But Portuguese law has changed since. The condition of "not having lost" the nationality, which paragraph (d) requires, has to be read in light of the laws that came after.
Organic Law no. 1/2004
In January 2004, Portugal passed Organic Law no. 1/2004. It provided that people who had lost Portuguese nationality by voluntarily acquiring a foreign one, under Law no. 2098/1959 and earlier legislation, recovered Portuguese nationality by operation of law. There was one condition: that no final annotation of loss of nationality was recorded in the Portuguese civil register.
This means a grandfather who naturalized as a Brazilian in the 1950s or 1960s, and never formally recorded that loss in Portugal, can be treated in law as a Portuguese citizen who never lost the nationality. Paragraph (d) asks for exactly that: a grandparent who is Portuguese by origin and did not lose it. The condition is met.
How to check: the grandfather's birth record
You need the grandfather's birth record, issued by the Portuguese civil registry office or the District Archive. In that document, look at the annotations. If there is no annotation of "loss of nationality" or similar wording, the path is generally still open.
For grandfathers born after 1910, you can order the record through the IRN's Civil Online portal at civilonline.mj.pt without leaving Brazil. For births before that, the record is probably in the District Archive of the grandfather's home district. The local civil registry office can confirm where the document is.
Pedro, from Curitiba, learned from family papers that his grandfather, born in Évora in 1929, became a naturalized Brazilian in 1968. He ordered his grandfather's birth record through Civil Online. It had no annotation of loss of nationality. Pedro's application went ahead under paragraph (d) with no obstacle.
If the record does carry an annotation of loss, the grandchild's direct path is blocked. The analysis then changes completely, because it depends on the date and the law in force at the time. In that case, it is worth consulting a lawyer who specializes in nationality law.
Linha Reta reviews the chain of documents and drafts the declaration of intent and the complete list of documents for your application. You get your grandfather's record from Portugal, make sure the chain is complete, and file the package with the IRN.