Complicating the response to the test announcement, there are few sanctions left to apply to North Korea, perhaps the world's second most-sanctioned country after Israel [the U.N. has voted 66 sanctions against Israel, all or most of which Israel ignores with little consequence]. The new North Korea sanctions bar all nations from selling the North expensive jewelry, yachts, luxury automobiles, and racing cars.
U.S. Ambassador to the U.N. Susan Rice said that, "taken together, these sanctions will bite, and bite hard."
That will depend on China, which has previously helped North Korea get around sanctions, seeming to have less concern for the country across the border having nuclear weapons than having it devolve into instability and chaos. So the current round of sanctions, like earlier ones, will have limited impact unless China should decide to limit its oil shipments, banking services, and other ongoing aid to North Korea.
Anyone Ready for an Act of War, like a Naval Blockade?
Another factor limiting the effectiveness of sanctions has been the unwillingness of the U.S. and other nations to enforce sanctions with a naval blockade, which would be an act of war. And it would be an act of war against a Chinese ally, enforced in the waters off the Chinese mainland.
The announced nuclear test in February came a few weeks after the Security Council had voted unanimously for a resolution in favor of tightening sanctions on North Korea for launching a three-stage rocket in December.
At this point, no one is claiming that North Korea actually has any nuclear warheads, or any actual capacity to deliver one anywhere.
But North Korean [DPRK] bristling continued on April 4, as an unnamed army official suggested that: