Jay Tea over at Wizbang! has a post up regarding the conditions under which the US might use nukes. Jay seems to think that the US would never use nukes except in retaliation, even though we've never signed on to the "no first use" idea. One thing he missed, though is the Nuclear Non-Proliferation Treaty and its side agreements. These are important to any understanding of the issue.
The US and other nuclear powers actually have agreed, as a codacil to the NPT, not to use nuclear weapons against any country that 1) is a signatory to the NPT, 2) does not have nuclear weapons (or certain other WMDs) and 3) is not closely allied in war with one that does. This is the carrot for the NPT. Note that first use against a nation with nukes is not ruled out in any way.
There is a flip side of this, naturally. North Korea by quitting the NPT and by developing nuclear weapons is no longer covered by this assurance. Iran, until the day they lock out the inspectors and/or is proven to have the Bomb, is covered.
What needs to be done is demonstrate the value of the NPT to those nations now considering, investigating, or pursuing nuclear weapons. Or rather, the significant detriment to their national security that possesssion of nukes brings to them. Failure to do so will lead to a very unstable world, as international stability seems to follow the inverse square of the number of nations with nukes.
If push comes to shove in North Korea, the demonstration of nuclear futility will likely be made there. There's really no way around it.