George W. Bush and Kim Jong-Un are two totally different situations. In the case of George W. Bush, there was not anyone, any country, or any group outside of the United States of America that could have stopped President Bush and the United States military. There are many countries and groups, first among them the United States, that could and would stop Kim Jong-Un from launching a pre-emptive war.
The United States, for the most part, had the money, military power, and the ability to launch a pre-emptive strike against just about any country it wanted to attack. Beyond that the United States had the political power, the military power, and the financial power to repel any retaliatory attack launched against it as a result of launching a pre-emptive strike against another nation. The United States has veto power at the United Nations. In addition, it seems to have a great deal of pull at both the International Monetary Fund (IMF) and the World Bank. Furthermore, it, once again, has a very large and powerful military and a fairly large amount of money.
North Korea, on the other hand, does not have those same advantages. North Korea is no where near as powerful as the United States within the United Nations. North Korea also lacks the United States' power in both the IMF and the World Bank. North Korea's military, along with the rest of the world's militaries, is no where near as large and powerful and America's military. Finally, North Korea does not have the financial power of the United States.
So, if North Korea launched a pre-emptive strike against any nation, especially South Korea or the United States, things would go badly for the North Koreans very shortly after the attack was launched. If they attacked the United States or South Korea they would most likely have war declared on them by the United States, South Korea, and much of the world. North Korea would then most likely be defeated in a short period of time. After the defeat, Kim Jong-Un would be removed from power and possibly jailed.
I am pretty sure Kim Jong-Un is well aware of what would happen if he lead his country to attack any other country. As a result, I am pretty sure he will not launch a pre-emptive strike against another nation.
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