There is no way to tie an identity to a bitcoin address. I can generate a million bitcoin address and send how much ever I want to all of them. Suppose a law comes out that bitcoins possessed by Indian citizens should be declared and taxes must be paid for possessing them... or suppose another law stating that if you are found in possession of bitcoins, you will be jailed / fined, etc. As absurd as it is, there is no "Indian" bitcoin address that is "mine" like how I can say about my bank account. A person can send bitcoins to ten different addresses. It can all come to me or it can come to ten different people. There is no way to identify who owns a bitcoin address. They don't reside in my computer or my or in my possession physically. Anyone possessing the private key of an address owns those bitcoins. Anyone in the world can have the private key to my wallet (if I choose to give them / get hacked). There is no way for a govt to figure that out. For banning for work, centralization is mandatory. A law that cannot be enforced is not a law. It is wishful thinking at most. Hence I think a law cannot come into effect like you are saying.
At most there can be a law forcing Indian exchanges to reveal the withdrawal addresses of their customers. But then what? Its transferred to another address... could be another address of mine... or it could be Bittrex or Kraken. By some magic, they were able to confirm that it was indeed a Bittrex account... and what... the Indian govt stating the new Indian law and demanding they confirm the identity of the account holder? Watch out for that big middle finger! You see where its going? At some point the Governments across the world will need to unite and become a centralized "authority", kinda like the UN for anything like that to happen. Even then all it takes to shatter that foundation is one country to make a killing by announcing "Hey, come over here and open your exchange here. I don't have any ties with the other networked countries".
So you see, the scenario you are talking cannot happen even if India was under military rule, simply because the law cannot be enforced. Its like saying all the people who like Salman Khan will be taxed. How on earth is a law like that going to get enforced? Just because I purchased the ticket does not mean I watched the movie. Just because I watched the movie does not mean I like the idiot. At most they can ban his movies (please do!), just like they can ban the operation of bitcoin exchanges operating inside India. But they cannot ban someone possessing bitcoins. Banning the exchanges will simply lead to a very lucrative black market for the commodity in India. People will rush to Indians to fill that price gap in approximately 3 seconds. Throughout history, anything that was banned, shoots up in market value, not down.
this is India, people find Jugaad easily. 
