Kim Jong Un, second from left, attends a banquet in Pyongyang this month to celebrate North Korea's latest nuclear test. (Yonhap/European Pressphoto Agency/EFE)

North Korea has been under United Nations sanctions since 2006. These sanctions have grown significantly stronger over time. Other nations and entities, including the United States and the European Union, also have imposed unilateral measures on Pyongyang in that period.

And yet, North Korea's nuclear weapons program has not only persisted but flourished. The country also remains a dictatorship, with one of the worst human rights records in the world. It seems obvious that sanctions on North Korea have failed — so far, at least.

It's worth asking why, with another round of punitive measures agreed upon. The U.N. Security Council imposed tougher sanctions on North Korea on Monday, prompting North Korea to warn that the United States would “suffer the greatest pain” because of its push for the new sanctions.

The good news is that there are two clear and logical theories for why existing sanctions on North Korea haven't worked. But there's bad news, too: At their core, the two theories are pretty different — and if both are to be believed, they may imply contradictory policies.

Theory one: Sanctions have not hit North Korea hard enough.

The idea behind this theory is easy to grasp: North Korea hasn't been hit hard enough by sanctions to steer it away from belligerence. Observers note that life in North Korea, in economic terms, appears to have improved significantly since 2006. “The sanctions were perfunctory,” former North Korean official Ri Jong Ho, who defected, told The Washington Post earlier this year.

This doesn't necessarily mean that the sanctions are not strict — notably, the measures imposed by the United Nations in August did away with precautions against causing humanitarian suffering. And North Korea's apparent economic resilience can't fully be attributed to the economic measures undertaken by Kim Jong Un, either, though those are important, too.

U.S. Ambassador to the United Nations Nikki Haley spoke after the U.N. Security Council voted on Sept. 11 to impose further economic sanctions against North Korea. (Reuters)

Instead, the biggest problem with the sanctions may be implementation. China and Russia, two of North Korea's most important trading partners, have often balked at fully implementing the sanctions. Even when China finally agreed to meet the U.N. cap on coal imports from North Korea last year, some suspected that Beijing was still dragging its feet.

Other countries may turn a blind eye, too. A recent U.N. report on North Korea's economy suggested that there was plenty of blame to go around. For example, when direct coal imports to China began to drop, Pyongyang began rerouting this coal to other countries, including Malaysia and Vietnam. The North Korean regime is also suspected of working on Syria's missile systems and sending military trainers to African nations, including Angola and Uganda.

“[A]s the sanctions regime expands, so does the scope of evasion,” the report's authors noted. But if this problem could be addressed, it might offer hope that sanctions could compel North Korea to change its behavior.

Theory two: North Korea's leadership doesn't care about sanctions.

A less hopeful theory posits that North Korea is impervious to sanctions because … well, basically, because it's North Korea. Consider it this way: Sanctions are designed to change a nation state's behavior through the use of economic pressure. The idea is generally that the country's leaders will ultimately decide that the economic cost of their behavior is too great and switch course.

But North Korea isn't like any other country. Its leadership may not operate the way we would expect it to. North Korea is one of the most closed-off dictatorships the world has seen. Even seasoned observers of autocratic states have expressed shock at the fervent adulation for the Kim dynasty in the country. Under such a system, public opinion seems to have little effect on Kim Jong Un.

“They'd rather eat grass than give up their nuclear program,” one high-profile proponent of this theory, Russian President Vladimir Putin, said recently.

Kim seems to view nuclear weapons as his only option against the United States. These weapons would not only help him avoid being overthrown like Libya's Moammar Gaddafi — a frequent reference point for North Korea — but could also get U.S. forces out of South Korea and perhaps even reunite the peninsula under Pyongyang's terms (sure, the latter scenario is unlikely, but who in North Korea would tell Kim that?).

In fact, after surviving the devastation of the Korean War and the famine during the 1990s, there is a sense among some North Korean officials that the sacrifices imposed by the sanctions — or, worse, war — might be worth it. “A lot of people would die,” one official recently told the New Yorker's Evan Osnos. “But not everyone would die.”

The problem.

Which of these theories is more accurate? It may not be possible to say definitively. Measuring the effectiveness of sanctions in any circumstances is almost always difficult, let alone with regard to a country as secretive and frequently duplicitous as North Korea. Meanwhile, we have little real understanding of how Kim makes his decisions and what his private feelings about sanctions are.

In some ways, both theories may be partially right. China has been reluctant to sign off on an oil embargo against North Korea, in part because it believes Pyongyang may view such a move as an existential threat and react in an unexpected way.

But the differing theories point toward a worrying ambiguity. If North Korea really is impervious to sanctions, imposing more such measures on the country could be a waste of time and perhaps even counterproductive. At the same time, if sanctions could actually change North Korea's behavior, the skepticism of powerful critics like Putin undermines that enterprise and bodes ill for their effectiveness.

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