Had a similar experience at Delhi, got in from KL on a Malaysian airlines flight, had a non connecting BA flight to London had to exit the airport and then reenter. Upon reentering I realised check in for BA flight wasn't open so I wished to go back outside for a cigarette. Indian security categorically wouldn't let me leave, I hadn't passed through security, hadn't checked in, I simply wanted to leave the terminal for short while.

Indian security and buerocracy is nothing short of a joke.