Once the papers of accessions were signed Kashmir belonged to India - the same way Bahawalpur and Chitral belonged to Pakistan once the accession was signed by their respective Kings. UN resolutions are no more valid and have been replaced by Shimla agreement.
Anyway lets not get into those things that are dead beaten on PDF since 2006.
Nothing is dead and beaten till it is. Nehru took the Kashmir issue to the UN, not Pakistan. The UN decided through a number of resolutions and Indian Occupied Kashmir is a disputed territory till the time Kashmiris are given their right to self determination. The UN resolutions are still valid till the Kashmir issue is amicably resolved.