This is an excellent article that litterally went under the radar by politico in april 2017
…In reality, some of them were accused by Obama’s own Justice Department of posing threats to national security. Three allegedly were part of an illegal procurement network supplying Iran with U.S.-made microelectronics with applications in surface-to-air and cruise missiles like the kind Tehran test-fired recently, prompting a still-escalating exchange of threats with the Trump administration. Another was serving an eight-year sentence for conspiring to supply Iran with satellite technology and hardware. As part of the deal, U.S. officials even dropped their demand for $10 million that a jury said the aerospace engineer illegally received from Tehran.
And in a series of unpublicized court filings, the Justice Department dropped charges and international arrest warrants against 14 other men, all of them fugitives. The administration didn’t disclose their names or what they were accused of doing, noting only in an unattributed, 152-word statement about the swap that the U.S. “also removed any Interpol red notices and dismissed any charges against 14 Iranians for whom it was assessed that extradition requests were unlikely to be successful.”
Three of the fugitives allegedly sought to lease Boeing aircraft for an Iranian airline that authorities say had supported Hezbollah, the U.S.-designated terrorist organization. A fourth, Behrouz Dolatzadeh, was charged with conspiring to buy thousands of U.S.-made assault rifles and illegally import them into Iran.
A fifth, Amin Ravan, was charged with smuggling U.S. military antennas to Hong Kong and Singapore for use in Iran. U.S. authorities also believe he was part of a procurement network providing Iran with high-tech components for an especially deadly type of IED used by Shiite militias to kill hundreds of American troops in Iraq.
The biggest fish, though, was Seyed Abolfazl Shahab Jamili, who had been charged with being part of a conspiracy that from 2005 to 2012 procured thousands of parts with nuclear applications for Iran via China. That included hundreds of U.S.-made sensors for the uranium enrichment centrifuges in Iran whose progress had prompted the nuclear deal talks in the first place.
When federal prosecutors and agents learned the true extent of the releases, many were shocked and angry. Some had spent years, if not decades, working to penetrate the global proliferation networks that allowed Iranian arms traders both to obtain crucial materials for Tehran’s illicit nuclear and ballistic missile programs and, in some cases, to provide dangerous materials to other countries.
Long read but very informative
https://
www.politico.com/story/2017/04/24/obama-iran-nuclear-deal-prisoner-release-236966