On March 9, the U.S. District Court in the southern district of New York reached a default judgment ordering Iran to pay some $10 billion to the relatives of victims of the terrorist attacks of Sept. 11, 2001, as well as to an insurance company. A default judgment is not a determination of guilt, or even a finding on the merits. But the ruling hints at one of the myriad risks of empowering an unpredictable regime with a violently anti-American ideological bent.This is a uniquely awkward time for a plaintiff to raise even the possibility of Iranian liability for the Sept. 11 terrorist attacks and to reach no meaningful conclusion. The United States is currently scrapping nearly all of its remaining sanctions against Iran as part of last year’s landmark nuclear deal—moves that could soon give the Islamic Republic access to the U.S. financial system and eventually strip nearly all uranium enrichment limits on the country’s nuclear program within the next 15 years.The judgment resulted from Iran’s failure to contest the case or even respond to the plaintiffs’ accusations that Iran and Hezbollah, Tehran’s Lebanese proxy, had facilitated the travel of several of the Sept. 11 hijackers and aided al-Qaida in the lead-up to the attacks. Notably, the same judge had issued a $6 billion default judgment against Iran, al-Qaida, and a number of other Sept. 11 conspirators in 2012, in a decision that was widely considered to be unenforceable and “symbolic.” (While there are various proposed mechanisms for compensating American plaintiffs in terror-related cases against Iran even in the absence of diplomatic relations between the two countries—including a congressionally mandated and taxpayer-maintained U.S. government fund—none are currently capable of financing a decision of that size. Meanwhile, the question of Iranian compensation for the victims of Hezbollah’s 1983 bombing of the U.S. Marine Barracks in Beirut still hasn’t been settled.)In court filings, the plaintiffs in the case have taken Iran’s unresponsiveness as added evidence of the regime’s involvement in the Sept. 11 plot. Given the still-cold and even adversarial state of U.S.-Iranian relations, even in the wake of a nuclear deal that is giving some $100 billion in sanctions relief to the regime, it would have been a major diplomatic breakthrough if Tehran had actually decided to contest the accusations against it. Court records include some incendiary claims about Iranian complicity in the attacks and of organizational ties between Hezbollah and the Sept. 11 terrorists themselves. But because Iran chose not to contest the case, the plaintiffs’ narrative of events went essentially unchallenged.In both their civil complaint and a series of expert affidavits, the plaintiffs allege that Iran aided in the movement of the Sept. 11 hijackers as they traveled between Iran and Afghanistan. Iran “ordered its border inspectors not to place telltale stamps in the passports of these future hijackers traveling to and from Afghanistan via Iran,” the plaintiffs’ complaint alleges.According to the 9/11 Commission Report, published in 2004, between eight and 10 of the 14 Saudi “muscle hijackers” who carried out of the attacks transited through Iran between October 2000 and February 2001. The Commission also found “strong evidence that Iran facilitated the transit of al-Qaida members into and out of Afghanistan before Sept. 11, and that some of these were future Sept. 11 hijackers.” While the plaintiffs never allege that Iran had specific foreknowledge of the Sept. 11 plot, they claim that al-Qaida operatives could not have traveled through Iranian territory—never mind received allegedly special treatment at the country’s borders—without the assistance of Iran’s various intelligence agencies.The plaintiffs’ more specific accusations have to do with the most notorious terrorist in Hezbollah history’s alleged involvement in the Sept. 11 plot. In an affidavit for the plaintiffs submitted in early 2011, ex-CIA officers Clare D. Lopez and Bruce Tefft claim that the “senior Hezbollah operative” referred to on pages 240 and 241 the 9/11 Commission Report is in fact Imad Mughniyah, Hezbollah’s secretive head of external operations, who was killed in a joint U.S.-Israeli operation in Damascus in 2008. Mughniyah was the mastermind of nearly three decades’ worth of deadly, world-spanning terror attacks, including the 1994 AMIA bombing in Argentina, the 1996 Khobar Towers attack in Saudi Arabia, the 1983 Kuwait embassy bombings and the bombings of the U.S. Marine barracks and U.S. embassy in Lebanon that same year.According to the plaintiffs’ finding of fact, which draws heavily on Lopez and Tefft’s affidavits, Mughniyah personally accompanied the future hijackers on flights to Lebanon and traveled to Saudi Arabia to “coordinate…the hijackers’ travel, their obtaining new Saudi passports and/or U.S. visas for the Sept. 11 operation, the hijackers’ security, and the operation’s security.”The 9/11 Commission Report cites several vague points of possible contact between Hezbollah operatives and the Sept. 11 hijackers, but it does not actually name Mughniyah or draw any substantial conclusions on the Iranian proxy’s knowledge of the plot:In October 2000, a senior operative of Hezbollah visited Saudi Arabia to coordinate activities there. He also planned to assist individuals in Saudi Arabia in traveling to Iran during November. A top Hezbollah commander and Saudi Hezbollah contacts were involved.\n\n\n\nAlso in October 2000, two future muscle hijackers, Mohand al Shehri and Hamza al Ghamdi, flew from Iran to Kuwait. In November, Ahmed al Ghamdi apparently flew to Beirut, traveling-perhaps by coincidence-on the same flight as a senior Hezbollah operative. Also in November, Salem al Hazmi apparently flew from Saudi Arabia to Beirut.\n\n\n\nIn mid-November, we believe, three of the future muscle hijackers, Wail al Shehri, Waleed al Shehri, and Ahmed al Nami, all of whom had obtained their U.S. visas in late October, traveled in a group from Saudi Arabia to Beirut and then onward to Iran. An associate of a senior Hezbollah operative was on the same flight that took the future hijackers to Iran. Hezbollah officials in Beirut and Iran were expecting the arrival of a group during the same time period. The travel of this group was important enough to merit the attention of senior figures in Hezbollah.\n\n\n\nLater in November, two future muscle hijackers, Satam al Suqami and Majed Moqed, flew into Iran from Bahrain. In February 2001, Khalid al Mihdhar may have taken a flight from Syria to Iran, and then traveled further within Iran to a point near the Afghan border.Lopez and Tefft are both decorated CIA veterans. Lopez, who is now the vice president for research and analysis at the controversial Reagan-era Pentagon official Frank Gaffney’s Center for Security Policy, spent 20 years as an overseas undercover operations officer and left the agency in 2000. Tefft was an undercover officer and station chief during a two-decade CIA career that ended in 1995. After the Sept. 11 attacks, Tefft worked as a counter-terror consultant contracted by the New York Police Department, but was accused of sending “hundreds” anti-Muslim emails to city law enforcement officials in a 2006 non-discrimination lawsuit.Their 2011 affidavit doesn’t constitute a smoking gun because it’s unclear exactly where the authors’ information is coming from. But it does include a single, tantalizing citation for pages of accusations against Hezbollah’s arch terrorist: “Mughniyah is discussed at length, infra, based on open source information, a confidential source and [redaction],”a footnote on page 27 of the affidavit reads. Elsewhere, the authors note that “The 9/11 Commission does not identify Imad Mughniyah … as the senior operative of Hizballah and top Hizballah commander,” before the text lapses into another redaction.The vagueness of the affidavit’s reasoning holds out the possibility that the authors’ sourcing is credible while making it difficult to figure out exactly what that sourcing really is. In context, it appears likely the claims about Mughniyah’s involvement in the Sept. 11 plot are based on information that came to the authors outside of official channels, after their agency careers had concluded. When reached for comment, Tefft said that he and Lopez’s affidavit reflected “a combination of what is in the open sources, and what we knew in the open sources that didn’t conflict with what we knew from our classified sources.” Their conclusions in the affidavit were also based on information from witnesses in the lawsuit “whose identity was withheld by the court itself to protect their safety,” according to Tefft. Lopez declined to comment on the affidavit.Which raises the question: Is it possible that Imad Mughniyah, who was arguably the world’s most wanted terrorist prior to the Sept. 11 attacks, could have actually visited Saudi Arabia in the run-up to Sept. 11? Although Mughniyah kept an incredibly low profile, he was known to have flown on commercial flights between Damascus and Tehran—and in an incident in the early 1990s, Mughniyah was on a commercial flight that stopped in Saudi Arabia, although he was not arrested during the layover. As part of an October 2000 federal plea agreement related to al-Qaida’s 1998 bombings of two U.S. embassies in east Africa, al-Qaida operative Ali Mohammad claimed that he “arranged security for a meeting in the Sudan between Mughaniyah, Hezbollah’s chief, and Bin Laden” in the early 1990s,” a summit in which the international terror bosses allegedly swapped notes on jihadi best practices.On the other hand, Mughniyah had ordered attacks in Saudi Arabia and would have been taking on an extraordinary personal risk in deliberately traveling there for any reason.Patrick Clawson, the director of research at the Washington Institute for Near East Policy and an expert on Iran who also submitted a plaintiffs’ affivadivt in the case, believes it was unnecessary for the plaintiffs to even raise the issue of Mugniyah’s involvement, since a government’s issuance of travel visas already constitutes materials support for terrorism under U.S. law. “I told the lawyers don’t go into speculating about this or that theory,” Clawson said. “As a matter of law, don’t get into that. You have very lock-solid evidence that Iranian support meets the standard under the law.”Thomas Joscelyn, a senior fellow at the Foundation for Defense of Democracies focusing on al-Qaida and international terror networks, says that it’s “plausible” based on his research of the links between Iran and Al Qaida that Mughniyah is one of the “senior Hezbollah operatives” named in the 9/11 Commission Report, but that he “can’t directly affirm that without seeing the actual evidence.” The documentary basis for the 9/11 Commission’s discussion of Hezbollah’s possible role in the Sept. 11 plot, which the report’s footnotes cryptically source to “intelligence reports, hijacker activities,” has not yet been made public.Philip Smyth, an expert on Shi’ite militant movements and adjunct fellow at the Washington Institute for Near East Policy, says that much of the al-Qaida-Hezbollah relationship in the immediate pre-Sept. 11 period is still shrouded in mystery. “A lot of this exists in a gray zone,” Smyth said of specific instances of cooperation in the years before the Sept. 11 attacks, adding that “there’s a lot of subterfuge that goes into Iran’s covert dealings and in how they counter the US in an ideological form and also in a more direct political form.”Inevitably, the substance of Iran’s relationship with al-Qaida—whether Mughniyah personally ferried Sept. 11 hijackers to Beirut, or whether the cooperation was somewhat vaguer than that—matters less than the fact that establishing there was actually a relationship between them. As Smyth notes, Iranian outreach to like-minded anti-American and anti-Israel Sunni groups was a priority even from the Ayatollah Khomenei’s time in power in the 1980s, and explains Tehran’s willingness to aid organizations like Palestinian Islamic Jihad and Hamas. And, according to the U.S. State Department’s citation of Iran as a state sponsor of terrorism, Iran refused to identify al-Qaida members in government custody, and “previously allowed AQ facilitators to operate a core facilitation pipeline through Iran since at least 2009, enabling AQ to move funds and fighters to South Asia and Syria.”The Iranian regime has shown a historical willingness to set aside sectarian disagreements with radical Sunni groups in the name of larger strategic goals: Iran was often at odds with the Taliban regime in neighboring Afghanistan but still aided the group in its fight against the U.S. military after the American-led invasion of the country. Iran aided militant Shi’ite sectarians in Iraq but also provided a safe haven for the rabidly anti-Shiite al-Qaida in Iraq leader Abu Musab al-Zarqawi in the early 2000s. Smyth added that in 2007, Iran and Assad-aided secular militant groups fought alongside Sunni jihadists in Lebanon against the Lebanese military.At one point, Iran’s view of warfare against the United States and its allies was ecumenical enough to apparently involve the country’s regime— however peripherally—in the deadliest terrorist attack of all time. Much has changed since then: The Syrian civil war has deepened the sectarian divide in the Middle East, Sunni radical groups like ISIS present a direct threat to Iran, and the United States and Iran are now partners in implementing last year’s nuclear deal.The question now facing the United States is exactly how much Iran has really has changed. Fifteen years ago, the regime’s affinity for Sunni jihadists and their destructive objectives may have played a role in the Sept. 11 attacks. And today, that regime—controlled by many of the same figures, and under the guidance of the same Supreme Leader, the Ayatollah Ali Khamenei, as in 2000—is $100 billion richer.***Like this article? Sign up for our Daily Digest to get Tablet Magazine’s new content in your inbox each morning.