The problem is that North Korea has been under the rule of Kim Jong Il (and his father before him) very long. The people are brainwashed, don't know what happens outside of their country and will be shot if they criticize the government. So inside the country, not much is gonna change.
Maybe you think the international community should act. There you have a point, but there really must be something important before you can get all countries to act and get involved in internal affairs of a county. And in the case of North Korea, the government will not listen. Then others have to get military involved and send their sons there to die in a war for the sake of people that probably won't thank them for it because they are so brainwashed. Also, Kim Jong Il has nukes that he probably will use on China, South Korea or Japan, so that these countries rather let the people of N korea suffer then have a war in which their own people will probably suffer.
Following the news.