Why is Article 370 Controversial

Why Special Status to J&k? 
There was an agreement between the princely states and the British government i.e Suzerainty called the Doctrine of Paramountcy but after the independence, almost all Princely states accepted to join India except one. Jammu and Kashmir were allowed to choose either India or Pakistan. It chose to be independent but in October 1947 Pakistan attacked a part of J&K and now J&K wanted support. Maharaja Hari Singh Signed an instrument of accession with India that specified three subjects i.e foreign affairs, defense, and communications on which J&K would transfer its power to the government of India. In July 1952, the NEHRU-ABDULLAH agreement was signed which gave special status to J&K and led to the adoption of article 370. 

Talking about the Provisions of Article 370 
It has its flag and its constitution. The center has no power to announce a financial emergency in Jammu and Kashmir. 
Article 356 - President's rule is not directly applicable in Jammu and Kashmir. Residuary Powers - where only the center can make laws is not applicable in Jammu and Kashmir. Even preventive detention is not applicable in Jammu and Kashmir. There are no fundamental duties and DPSP in J&K. Right to the property is applicable and citizens from any other state of India cannot buy property in J&K. 

Is the Abrogation of Article 370 constitutionally right?
According to Article 370 of the Indian constitution, though it's written as Temporary Transient and special provisions it should be considered as permanent because article 370 can be abrogated or amended only upon the recommendation of the state's constituent assembly but the state's constituent assembly was dissolved on 25th January 1957. This article should be considered as a permanent feature of the Indian Constitution but with accordance to  presidential order 2019, The expression "Constituent Assembly '' was changed to "Legislative Assembly '' and so Article 370 is Abrogated. 

Current Status:- 
This state of Jammu and Kashmir is now converted into two union territories i.e union territory of Jammu and Kashmir and the union territory of Ladakh. On the night of 30th October 2019, the president's rule under Article 356 was ended in Jammu and Kashmir. The president ordered that he will be ruling the union territory of Jammu and Kashmir directly until the legislative assembly of Jammu and Kashmir is constituted. The center is trying to restore the full statehood of Jammu and Kashmir after the completion of the delimitation process.