In the Shiva Trilogy's final book Chief Vasudev Gopal threatens Meluha and warns them that they (Shiva's side) would not hesitate to use Daivi Astras despite knowing about the presence of Lord Bhrigu (on Somras' side) who knows about the Daivi Astra ban by Lord Rudra?
So why would Chief Vasudev Gopal think that he can bluff about using the Pashupatiastra?