It's an interesting question - these days I think there is a great deal of resistance to go down the nuclear route by any developed nation, simply because there are other options - through 'coalition' invasion and suchlike which are far more preferable than indiscriminate nuking especially given the vastly superior military capabilities of the developed nations to any of the potential 'rogue' states.
There wouldn't be any point in launching a retaliatory nuclear strike on country without a nuclear weapons programme as they would no longer pose a nuclear threat, however, military action would most definitely be in order.