Looks like you don't get it at all. ALL 500 plus Princely States in India were sovereign and each was free to have its own Constitution, laws, assemblies etc. But they still recognized British SUZERAINTY over them. That lapsed on August 15th, 1947 so technically ALL Princely states in India and Pak became independent. A treaty of accession did not necessarily amount to a merger. It ensured the rulers of Princely States would keep their titles and be paid a privy purse.
@Joe Shearer will explain more to you.
Manipur's case is totally different than your typical mainland indian states;
Manipur State Assembly rejected the Merger Agreement
The 4th sitting of the 3rd session of the Manipur State Assembly in its session held at the Johnston School on 28th September, 1949 at 2.30.p.m rejected the “Merger Agreement signed on 21st September 1949” and declared the Merger Agreement invalid as the powers and authorities of King had been vested with the Manipur State Assembly.
The Merger Agreement was neither approved by his Council of Ministers nor ratified by the Manipur State Legislative Assembly.
The weakness of the Agreement lies also in the fact that the people of Manipur did not give consent in any form to the Merger Agreement as no referendum was held on that issue. Further, the Merger Agreement was neither approved by his Council of Ministers nor ratified by the Manipur State Legislative Assembly. Therefore, the Merger Agreement was illegal.
The Indian Independence Act, 1947, Section 9(5) states that
“ No order shall be made under this section, by the Governor of any Province, after the appointed day, or, by the Governor-General, after the thirty-first day of March, nineteen hundred and forty-eight ( 31 March, 1948), or such earlier date as may be determined, in the case of either Dominion,. by “any law of the Legislature of that Dominion.”.
However, violating the provisions of the Indian Independence Act, 1947, para 9(5), Governor General of India issued an order on 15 October 1949 declaring that ‘the Ministers’ in Manipur State shall cease to function and the Legislature’ of the State shall stand ‘dissolved’ citing Sections 3 and 4 of the Extra Provincial Jurisdiction Act, 1947 (Act XLVII of 1947). This is in violation of Independence Act, 1947 and again illegal.
The Merged States (Laws)- Act, 1949 Act no. 59 of 1949 dated 26th December, 1949 is Illegal
The Merged States (Laws)- Act, 1949 Act no. 59 of 1949 dated 26th December, 1949 is an Act to extend certain laws to certain areas administered as parts of Governors’ Provinces or as Chief Commissioners’ Provinces. The legality of this Act is questionable as it has been passed after actual merger of Manipur to dominion India has already taken place illegally.
Why should a highly responsible democratic Government of India indulged in such deceitful action in order to provide legality to a highly illegal action committed earlier. It is just like hanging somebody first and then issuing the hanging order later on.
As per the Notification issued by the Government of India, Ministry of Law, dated the 22 January 1950, paras 1(1) (2), 2(1) the States Merger (Chief Commissioners’ Provinces) Order, 1950 shall come into force only with effect from the 23 January, 1950. Therefore the State of Manipur should have become administered under a Chief Commissioner only from 23 January, 1950 onwards and as such the orders issued by the Ministry of States, New Delhi, dated the 15 October 1949 hurriedly merging Manipur with the Dominion of India was illegal.
Further, the said Manipur Merger Agreement was not done under any Act or Law or Parliamentary Resolution. It was done hastily by the decision of Sri Prakasa, Governor of Assam, V.P. Menon, Advisor to the Government of India violating international laws, the Manipur State Constitution Act-1947 and the Indian Independence Act-1947.
Further, the said Manipur Merger Agreement was not done under any prescribed format under any Act or Rule. It was done on a draft hastily prepared and amended many times by Nari Rustomji, Advisor to the Governor of Assam, V.P. Menon, Advisor to the Government of India. It should be rendered invalid.