North Korea bypassed a U.N. fuel cap meant to hinder its nuclear program by buying cheap Taiwanese oil from a sophisticated smuggling network for years, according to a new report.

The report, published by the Royal United Services Institute (RUSI) and the Center for Advanced Defense Studies (C4ADS) in conjunction with The New York Times, suggests that a series of ships and front companies affiliated with a multinational conglomerate called Winson Group smuggled fuel to North Korea since 2017, when the U.N. fuel cap was first announced. In a statement to NK Pro, the Winson