Dual citizenship is applicable to A person whose citizenship of Sri Lanka has ceased under section 19, 20 or 21 of the Citizenship Act, No 18 of 1948 or a person whose Citizenship of Sri Lanka is likely to cease.
Resumption – Section 19(2) of the said Act makes provisions in respect of a person whose citizenship of Sri Lanka has ceased due to obtaining of citizenship in another country and who thereafter desires to resume the status of a citizen of Sri Lanka, or
Retention – Section 19(3) of the said act makes provisions in respect of person who is having a desire to obtain citizenship in another country, while intends to retain the citizenship of Sri Lanka.
Applications for dual citizenship by Sri Lankan expatriates in South America could be submitted directly to the Citizenship Division of the Department of Immigration and Emigration of Sri Lanka or to the Sri Lanka Embassy in Brasilia, Brazil in person along with relevant supportive documents.
More details at the official website of the Department of Immigration and Emigration of Sri Lanka.