Nukes for the North
North Korea conducts a nuclear test and America's non-proliferation policy is officially a mess. At this point, there are two kinds of questions one can ask. One set is about non-proliferation policy as such and what one needs to do to get it back on track. Another specifically concerns North Korea. When we were talking DPRK on BloggingHeads, Dan Drezner made the point that there actually are a couple of steps that could be taken that really would stand a decent chance of bringing the Pyongyang regime to the breaking point, namely an end to the money coming in from South Korea under the "sunshine policy" and a shift in Chinese policy aimed at facilitating, rather than preventing, DPRK residents from crossing the border into China.
The trouble is that nobody especially wants to see the North Korean regime actually collapse. Certainly the South Koreans aren't looking forward to needing to assume responsibility for a relatively large and incredibly impoverished country. The reuinification of Germany has created a lot of economic and social problems for the former West Germany, and this would be like that situation on steroids. China, meanwhile, isn't enthusiastic about the idea of giant cross-border refugee flows. The issue for US policymakers then becomes whether there's anything we might be able to offer in terms of assistance that would make Seoul and Beijing more comfortable with ending their efforts to prop up North Korea's government, and whether that's something we would actually want to offer.
Similarly, would we actually want to see North Korea collapse, or would that make the nuclear situation even worse since, presumably, we don't want to see those weapons and material floating around.