His concern is about going to jail. I've previously read about similar cases of cards getting blocked due to them being used for international transactions prohibited under FEMA but I've not heard of anyone going to jail for it; nonetheless, if that's a concern, then it might be time to consult a decent lawyer.
This is the "free" country we live in, where a person can't even do something that doesn't hurt anyone else, with HIS OWN money! Whether it's forex trading or gambling or whatever, so long as you're not hurting someone else or stealing from or defrauding someone, people should be free to do what they want involving mutual voluntary interaction between other free people, that's true freedom!