18 of 1948 was a controversial law passed by the Ceylon Parliament which did not grant citizenship to Indian Tamils, who were 11% of the population.
There was real fear amongst the Indian Tamils that once Ceylon obtained independence, the Sinhalese, who constituted 69.4% of the population, would take steps to remove them from the country.
[1] The Bill stipulated that anyone wishing to obtain citizenship had to prove that their father was born in Ceylon i.e. that they were at least third generation immigrants.
[2] The Bill was passed by Parliament on 20 August 1948 and became law on 15 November 1948, just 285 days after Ceylon had gained independence from Britain.
They had a habit of periodically returning to India, thereby interrupting their residence in Ceylon, and most could not meet the income qualification.
[4] Upcountry Indian Tamils influenced the result in 20 other constituencies, very often voting for the opposition Sinhalese leftist parties.
[1][5] On 30 October 1964 Indian Prime Minister Lal Shastri and Ceylon Prime Minister Sirimavo Bandaranaike signed the Sirima-Shastri Pact (also known as the Indo-Ceylon Agreement) under which India agreed to the repatriation of 525,000 Indian Tamils.
[1][6] On 28 June 1974 Indian Prime Minister Indira Gandhi and Ceylon Prime Minister Sirimavo Bandaranaike signed the Sirimavo-Gandhi Pact under which India and Sri Lanka agreed to grant citizenship to the 150,000 Indian Tamils whose status was left unresolved by the Sirima-Shastri Pact.