Seyed Hossein Mousavian is an ex-Iranian diplomat whose tenure in Germany coincided with the regime’s assassination of four dissidents on German soil. Yet he currently lives in comfort in the United States. Does he belong here? That’s the question raised by a number of prominent Iranian-Americans in a recent letter to Attorney General Bill Barr.

The details are grim. Late evening on Sept. 17, 1992, four men were dining together in the backroom of the Mykonos restaurant, a Greek eatery in central Berlin. They were Iranian exiles who had gathered to meet a prominent Kurdish opponent of the Tehran regime.

At 10:47 pm, two masked assailants entered the restaurant and began firing at the men, killing all four. The killers immediately fled the scene. The German government launched an investigation, which led to the identification of an Iranian intelligence officer, three Hezbollah jihadists and an Iranian-German businessman who jointly coordinated the assassination.

After a lengthy trial, Berlin’s highest court concluded in April 1997 that the plot had been hatched at the highest echelons of power in Tehran, including by Supreme Leader Ayatollah Ali Khamenei, President Akbar Hashemi Rafsanjani, Foreign Minister Ali Akbar Velayati and Intelligence Minister Ali Fallahian.

Seyed Hossein Mousavian was Iran’s ambassador at the time. Running interference for the regime, he dismissed the charges as a “joke” and predicted that “the judges are sure to vote in Iran’s favor.” The judges didn’t, in fact, rule in Iran’s favor, and the German government eventually requested the removal of Moussavian along with others attached to the intelligence section of the Iranian embassy. The Germans expelled four Iranian diplomats, and Mousavian quietly decamped on his own accord.

After his return, Mousavian headed the foreign-relations committee of Iran’s Supreme National Security Council during Mohammad Khatami’s presidency. Then, in 2009, he surfaced in the United States as a “visiting scholar” at Princeton University’s Woodrow Wilson School of Public and International Affairs.

During the Obama presidency, Mousavian was a constant fixture at various forums organized by Washington think tanks, and he frequently gave interviews on news networks. He consistently defended the Tehran regime, much as he had run interference for the mullahs while serving in Germany during the Mykonos affair. Even today, he continues to write opinion pieces defending the interests of the Iranian regime and criticizing Team Trump’s foreign policy.

But now that President Trump has withdrawn Washington from the nuclear deal, it makes no sense for Mousavian to remain on US soil. Hence our letter urging Barr to investigate his presence. As we write in the letter, “Mousavian’s presence on US soil serves no purpose but to promote the ideology and interests of America’s staunchest enemy and sow fear and division within the Iranian-American community.”

With his close ties to the Iranian regime, and diplomatic role at a time when Tehran was murdering dissidents abroad, Mousavian is a menacing presence to Iranian-Americans. How did he come to be here? And how does he get to stay? And what role is he playing? Team Trump must find out.

Reza Behrouz is an Iranian-American physician and dissident based in San Antonio, Texas. Peter Kohanloo is president of Iranian-American Majority.