Is forex trading legal?

I know that you can trade any inr pair in nse currency derivatives. But what about USD/EUR pair, etc. There are many us based brokers like easyforex, alpari, etc. Few years back credit card companies had sent an email saying that it is illegal to do so.

However, these days I have started receiving calls from such companies from Indian locations saying that it is now legal to do so. Can anybody confirm? These markets are fit 24 hours and highly liquid and hence advantageous.