WASHINGTON – Last fall, Hugh Griffiths received startling new evidence that North Korea was violating global economic sanctions: a photograph of Kim Jong Un emerging from a sleek, black Rolls-Royce Phantom limousine, on his way to a meeting with U.S. Secretary of State Mike Pompeo.

United Nations' sanctions bar North Korea from purchasing certain luxury goods – such as jewelry, yachts and limos, like the one Kim used to ferry him around Pyongyang last October, when Pompeo visited to press Kim to follow through on his pledge to relinquish North Korea's nuclear arsenal.

Until recently, Griffiths was coordinator of the United Nations' panel devoted to documenting North Korea's clandestine purchase and sale of banned goods – from multi-million-dollar petroleum transfers to a batch of suspected Belarusian vodka. The pictures of Kim stepping out of the Rolls-Royce limo opened a new line of inquiry for Griffiths and his team at the U.N., one that was both promising and troubling.

Troubling because if Kim could evade the global sanctions network to sneak in something as big as a limousine, the North Koreans were almost certainly smuggling in more pernicious goods as well.

"That's what was going on in my mind," Griffiths told USA TODAY in a recent interview. His term at the U.N. expired this summer, and he spoke via phone from England. He is an expert in transportation trafficking and clandestine political economies who previously worked for other governments and research organizations in Eastern Europe and elsewhere.

"If you can smuggle luxury limos into North Korea, which is done by shipping container, that means you can smuggle in smaller components – dual-use items for ballistic and nuclear programs … That's the really worrying thing."

A 'consistent pattern of extravagance'

The Trump administration has successfully pushed to tighten U.N. sanctions on North Korea, winning support in 2017 for a ban on the country's coal and other exports. Nikki Haley, then Trump's ambassador to the U.N., called the measures "the most stringent set of sanctions on any country in a generation."

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Trump has touted his "maximum pressure" campaign as a key factor in Kim's decision to negotiate over North Korea's nuclear arsenal. Two previous Trump-Kim summits, first in Singapore last summer and then in Hanoi, Vietnam, this year, have not yet yielded any concrete steps by North Korea to relinquish its weapons.

And the North Koreans have found many ways to skirt that "maximum pressure" campaign, according to the U.N. investigators.

"The country continues to defy Security Council resolutions through a massive increase in illegal ship-to-ship transfers of petroleum products and coal," the U.N. concluded in a March report, the last before Griffiths' departure. "These violations render the latest United Nations sanctions ineffective by flouting the caps on the import of petroleum products and crude oil."

Sung-Yon Lee, a Korean Studies professor at Tufts University's Fletcher School, said Kim spends $650 million to $700 million a year importing luxury goods, from top-shelf liquor to ski jets, according to data from South Korea's intelligence agencies.

"It’s a consistent pattern of extravagance," he said. The Chinese are "the biggest culprits" in enabling North Korea to evade sanctions.

"But when it comes to non-compliance and non-enforcement, much of the world, including the U.S., is to be blamed as well," Lee added. "No one relishes doing the hard work of sanctions enforcement. But it's the one non-lethal, legitimate, effective diplomatic arrow in the U.S. quiver."

On Sunday, Trump met with Kim at the border that separates North and South Korea in a splashy gambit to restart the stalled negotiations. The two leaders agreed to send negotiating teams back to the table, although there were no specifics announced.

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Griffiths said Kim's decision to flaunt his new limo during last fall's meeting with Pompeo – even as the two were meeting to negotiate a potential nuclear deal – was a deliberate signal to the U.S. and the rest of the international community: He can thumb his nose at the sanctions.

"It's very important to identify how this Rolls-Royce got there because Chairman Kim is clearly trying to send a message that he's taking the sanctions with a pinch of salt," he said. And the sanctions, he added, "represent the only real threat to Chairman Kim's current trajectory."

Hunting a phantom limousine

But Kim's brazen move also offered the U.N. team a tantalizing new lead. The U.N. experts had previously traced another North Korean limo to a Chinese businessman and made inroads into closing off that smuggling line, and Griffiths hoped for the same result this time.

Their first step was simple: take the public images coming out of Pyongyang and look for any stand-out identifiers on the luxury vehicle, which carries a price tag of at least $450,000, according to Car and Driver magazine.

The automakers' trademark "R" was clearly visible on the hub cap, and the U.N. team found a few other distinguishing features as well. Off went an inquiry to Rolls-Royce's manufacturer.

The company offered a limited response: The vehicle was probably made between August 2012 and February 2017 at its facility in England.

A spokesman for Rolls-Royce Motor Cars declined to respond to USA TODAY's questions, including how many such vehicles were manufactured in that time period and why it was not able to provide further identifying information.

"We have responded fully to all questions put to us by the authorities at the U.N. and have no further comment," Andrew Ball, the spokesman, said in an email.

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Griffiths said it was a far different answer than he'd gotten from Mercedes-Benz when the panel tried to track several of that automaker’s limousines in 2015 and 2016.

"Mercedes-Benz went the extra mile to look into their databases and through a process of elimination, identify the limousines in question," he told USA TODAY.

That allowed the U.N. investigators to find the last company to have the Mercedes' limos before they ended up in North Korea. They determined that those limos were transported via a shipping container from the port of Long Beach, California, to Dalian, China, at the direction of George Ma, a Chinese businessman, according to the U.N. report.

A 2016 U.N. report said Ma's company had previously been involved in shipping "arms-related material" to the Republic of the Congo. Ma did not respond to an email seeking comment.

In March, the Trump administration slapped new sanctions on one of the firms that shipped the Mercedes, Liaoning Danxing International Forwarding Co. "Liaoning Danxing routinely used deceptive practices that enabled EU-based North Korean procurement officials to operate and purchase goods for the DPRK regime," Treasury said in its March announcement. The Democratic People's Republic of Korea is the official name for North Korea.

"At least with the Mercedes, the panel fingered Liaoning Danxing" and publicly named Ma – helping to close off that pathway for smuggling items to and from North Korea, Griffiths said.

But the probe into the Rolls-Royce appears to have stalled. Although the U.N. panel is continuing its investigation, Griffiths said it's hard to make headway without the vehicle's identification information.

A 'shiny object' for propaganda?

And now, another new limo has been spotted in North Korea: earlier this year, Kim was seen riding in an armored Mercedes-Maybach S600, which costs at least $500,000, according to The Drive, an automotive news outlet.

"There's an established system by which these prohibited luxury goods are being smuggled in," said Griffiths.

Joshua Stanton, a lawyer and blogger who has helped Congress draft North Korea sanctions legislation, agreed that the appearance of the limo signals a troubling loophole in enforcement. But he said it's by no means an indication that the sanctions are ineffective.

Rather than being a snub at the sanctions, Stanton said Kim is using the limo as a "shiny object" to disguise just how devastating the sanctions have been.

"It's a manipulation," said Stanton. "They are absolutely trying to project to the world that the sanctions don’t work – when in fact, the sanctions that really matter are the financial sanctions, and there is significant evidence that they are working."

He said there are indications that rich and poor North Koreans are struggling.

A U.N. assessment released in May found that more than 10 million North Koreans were "suffering 'severe food shortages' after the worst harvest in a decade."

Stanton said there is also evidence that North Korean government agencies are competing for diminishing resources and "the elite upper-classes in Pyongyang, who had lived like oligarchs, are showing signs of financial distress."

The sanctions on luxury goods are important "because of the message they send to the world," he added, " ... but the North Koreans messaging the world in their own way here."