Sikkim had retained guarantee of independence from Britain when she became independent, and such guarantees were transferred to the Indian government when it gained independence in 1947. A popular vote for Sikkim to join the Indian Union Failed and Indian Prime Minister Jawaharlal Nehru agreed to a special protectorate status for Sikkim. Sikkim was to be a tributary of India, in which India controlled its external defence, diplomacy and communication.
A treaty was made between India and Sikkim in 1950, in the interest of Prime Minister Jawaharlal Nehru. That Indo-Sikkim treaty gave Sikkim an Indian protectorate status. Sikkim came under the suzeraint of India, which controlled its external affairs, etc. but Sikkim otherwise retained administrative autonomy.
A State council was established in 1953 to allow for constitutional government under the Chogyal. Meanwhile, the Sikkim National Congress demanded fresh elections and greater representation for Nepalis in Sikkim.PaldenThondupNamgyal, the Chogyal at the time proved to be extremely unpopular with the people. In 1973, riots in front of the Chogyal’s palace led to a formal request for protection from India.
In 1975, the Prime Minister of Sikkim appealed to the Indian Parliament for Sikkim to become a state of India. In April of that year, the Indian Army took over the city of Gangtok and disarmed the Chogyal’s palace guards. Thereafter, a referendum was held in which 97.5% of voters supported abolishing the monarchy, effectively approving union with India. Although the union was presented as the will of the people by the Indian authorities, the merger was widely criticized as an annexation and India was accused of exploiting the ethnic divide and rigging the referendum.
On 16 May 1975, Sikkim became the 22nd state of the Union, and the monarchy was abolished.
To enable the incorporation of the new state, the Indian Parliament amended the Indian Constitution. First, the 35th Amendment laid down a set of conditions that made Sikkim an “Associate State”, a special designation not used by any other state. Later, the 36th Amendment repealed the 35th Amendment, and made Sikkim a full state, adding its name to the First Scheduled of the Constitution.