The latest UN sanctions, passed in response to two tests of intercontinental ballistic missiles in July, are perhaps the strongest ever enacted against the country: They call for a total ban on North Korea’s major exports, including coal, iron and iron ore, lead and lead ore, and seafood. They also expand the definition of the kinds of companies that can be classified as financial institutions—an important step to battle those firms that provide Pyongyang access to money—and limit the number of North Korean workers overseas, who remain a valuable source of foreign exchange. At the same time, they attempt to strengthen some prohibitions on port calls by vessels that have been previously involved in illicit trade, Snyder told me.

“Those restrictions are already pretty strong but there’s an additional effort on that front,” he said.

Nephew, the former State Department official who contributes to the North Korea-focused website 38 North, said the challenge remains enforcement, and the degree to which states take it seriously.

“So you now have a set of restrictions on what people can buy from North Korea. Are they actually going to hold to that? And are they going to inspect ships and cargo containers and so forth when they are coming from North Korea to prove that, in fact, they aren’t breaking those terms?” Nephew said. “Those are the problems that have bedeviled UN sanctions for quite a long time—and North Korea sanctions in particular.”

The new UN sanctions have been advertised as particularly severe based on estimates that they will cost North Korea $1 billion a year—a third of its annual export revenue. But Snyder pointed out that much of the assessment of the value of trade with North Korea is based on officially reported trade statistics. North Korea does not maintain these. China, which accounts for 90 percent of trade with the North, simply moves some transactions off the books while reporting others. There is simply no way to measure North Korea’s trade volume accurately—and thus no way to measure the true impact of the new financial penalties.

“By definition what we don’t know is what is not reported,” Snyder said. “People who go to Pyongyang and ask themselves the question: ‘Gosh, it seems like there’s a lot of liquidity here. Where is the capital coming from?’ I think part of the answer to that question is that not everything that goes into North Korea is officially recorded.”

For example, Snyder said: “We’ve seen the Chinese stop recording oil exports to North Korea,” Snyder told me, though “I think the widespread presumption is that the supply from China to North Korea has continued. Circumstantial evidence for the idea that they have continued is that there has been discussion in the run-up to this resolution [on the new UN sanctions] to implementing a petroleum trade ban. That does not appear in the resolution.”