India wants to ban international VoIP calls
India wants to ban VoIP because Caller Line Identification (CLI) data may not be available. The idea that CLI addresses the need to identify the caller is nonsense because CLI can easily be spoofed.
And for VoIP, it can just be tunneled. The terrorists will want to talk peer-to-peer and not terminate or originate calls via a PSTS-gated VoIP provider and they have ample options for how to do this.
Given the ease with which peers can conduct a private conversation on an IP network, the Indian authorities would probably do better to focus on leveraging what they can with the law as it applies to the existing PSTN.