Even as Kim's authoritarian regime appears to be taking steps to thaw its hostile relations with other world powers, Griffiths said UN member states have been able to monitor five to 10 sanction-defying trades each month.
As long as the ships continue to switch off their trackers, it's extremely difficult for the UN to monitor the petroleum product trades.
"It's impossible to physically detect these transfers because they switch off their AIS and they go dark and we can no longer see what they're doing," Griffiths said.
As for North Korea itself, Griffiths said the country still regards the Security Council as illegitimate.
"North Korean tankers are now always dark," Griffiths said.
The most recent report from the council's panel of experts on North Korea concluded that the country made $200 million in ship-to-ship transfers in the first nine months of 2017.
Griffiths said that despite North Korea's sudden warmth toward its southern neighbor, the transfers have continued. He said his team has witnessed a $40 million transfer in just one network within the past six months.
And even with an increase in talk of peace initiatives — including the prospect of a face-to-face meeting between Kim and President Donald Trump — Griffiths isn't so sure that denuclearization is on the way.
The UN coordinator noted that Kim, in his 2018 New Year's address, said that sanctions were indeed having an effect. "But another thing he talked about was the mass production of nuclear weapons. And that is something that is extremely difficult for our panel to track, and it's something I'm concerned about," Griffiths said.
Nuclear missile launch tests are understandably easy to track. But the assembly of nuclear weapons, which could be taking place in covered or underground facilities, is far more difficult to monitor.
"Some of this is above my pay grade," Griffiths cautioned, "but I think [with] the statements made by chairman Kim Jong Un about mass production, it would be very important to get into these sites and to see what's happening there."