Hagia Sophia was constructed as a Cathedral in Constantinople (now Istanbul) in 6th century by Byzantine emperor, Justinian I. In 1456, when Constantinople fell to the Ottoman empire, it was turned into a mosque. It was custom at that time, especially of Muslims, that when they captured enemy territory they would use it for their own purposes. Later on, when the founder of secular Turkey, Mustafa Kemal Ataturk, came into power he shut down the mosque and turned it into a museum in an attempt to make the country more secular. 

Now it was the decision of Turkey’s highest court which converted it to the same position of a mosque on the request of President Erdogan. Therefore Turkey being a sovereign state has the right to enjoy complete sovereignty over it as it is the most important feature of an independent state under international law. Why should desi liberals mourn the reconversion into a mosque? Why is this being criticized? Does he need to ask before doing anything within his territory?