<P> The demand for responsible government continued and the SSC launched a civil disobedience movement . The Chogyal Palden Thondup Namgyal asked India for help in quelling the movement, which was offered in the form of a small military police force and an Indian Dewan . In 1950, a treaty was agreed between India and Sikkim which gave Sikkim the status of an Indian protectorate . Sikkim came under the suzerainty of India, which controlled its external affairs, defence, diplomacy and communications . In other respects, Sikkim retained administrative autonomy . </P> <P> A state council was established in 1953 to allow for constitutional government under the Chogyal . Despite pressures from an India "bent on annexation", Chogyal Palden Thondup Namgyal was able to preserve autonomy and shape a "model Asian state" where the literacy rate and per capita income were twice as high as neighbouring Nepal, Bhutan and India . Meanwhile, the India - backed Sikkim National Congress demanded fresh elections and greater representation for Nepalis in Sikkim . People marched on the palace against the monarchy . In 1973, antiroyalist riots took place in front of the Chogyal's palace . </P> <P> 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 per cent of voters supported abolishing the monarchy, effectively approving union with India . India is said to have stationed 20,000--40,000 troops in a country of only 200,000 during the referendum . On 16 May 1975, Sikkim became the 22nd state of the Indian 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 . A month later, the 36th Amendment repealed the 35th Amendment, and made Sikkim a full state, adding its name to the First Schedule of the Constitution . </P> <P> In 2000, the seventeenth Karmapa, Urgyen Trinley Dorje, who had been confirmed by the Dalai Lama and accepted as a tulku by the Chinese government, escaped from Tibet, seeking to return to the Rumtek Monastery in Sikkim . Chinese officials were in a quandary on this issue, as any protests to India would mean an explicit endorsement of India's governance of Sikkim, which China still recognised as an independent state occupied by India . The Chinese government eventually recognised Sikkim as an Indian state in 2003, on the condition that India officially recognise Tibet as a part of China; New Delhi had originally accepted Tibet as a part of China in 1953 during the government of Jawaharlal Nehru . The 2003 agreement led to a thaw in Sino - Indian relations, and on 6 July 2006, the Sikkimese Himalayan pass of Nathu La was opened to cross-border trade, becoming the first open border between India and China . The pass, which had previously been closed since the 1962 Sino - Indian War, was an offshoot of the ancient Silk Road . </P>

Sikkim was made an integral part of india under which amendment