Despite the headlines generated by the gold trade and leaked report, the Turkish government insisted that everything was above board. The Obama administration seemed to echo this sentiment, saying that the gold trade had slipped through a legal loophole (a loophole the White House inexplicably left open for an additional six months, even after the problem was flagged). We soon learned Ankara’s political motivations: The gold trade helped boost Turkey’s flagging export numbers at a moment when those numbers might have hurt President Recep Tayyip Erdogan’s chances for reelection. Zarrab, who became fabulously wealthy by taking a percentage from every transaction (he later estimated his take at $150 million), even received a reward for his efforts from a Turkish trade association in 2015, with Erdogan applauding from the audience.

But it all came to an abrupt halt last March, when Zarrab inexplicably brought his family to America for a vacation at Disney World. With the 2015 nuclear deal in effect, he may have believed that the sanctions laws he violated before the deal were no longer in force. Some suggest that Zarrab was trying to flee Iranian justice, particularly as the regime came to grasp just how much he skimmed off the top. Either way, when he arrived in Florida, U.S. authorities arrested him for engaging in conspiracies to violate sanctions, commit bank fraud, and launder money.

It was about time. For three years, my colleagues and I had been briefing the Treasury Department, the State Department, and Congressional offices. We had tracked the export data (which, remarkably, Turkey did not hide), showing an astronomical spike in Turkish gold exports. We identified the companies and players, with the help of the 2014 prosecutor’s report. It was painstaking work, but it was all out there in open sources for a think tank like ours to document.

Yet, it was an inconvenient moment to reveal unsavory truths about Iran, amid the push for the nuclear agreement. Nor did anyone, Democrat or Republican, want to touch the third rail of relations with Turkey, a NATO ally that had recently begun backing terrorist groups like Hamas (which still maintains a disturbing presence in Turkey) and a range of Sunni jihadi groups fighting the Assad regime in Syria (including al-Qaeda’s affiliate, according to senior U.S. government officials we interviewed). Stable allies in the Muslim world were scarce, and decision-makers seemed reluctant to take any chances with Ankara.

It may also have been difficult for officials to hear that the sanctions tools we have in place to prevent bad actors from moving money are just that—tools. Without intense vigilance and enforcement, there is ample opportunity for Iran and other sanctioned countries to find workarounds. But if we’re going to follow the money, we’d better be prepared to follow it to the most inconvenient places.