-- From Sept. 11, 2001, until now, not a single American has been killed in a terrorist act on American soil by anyone who entered the United States as a refugee.

-- Of 12 persons who carried out lethal terror attacks after 9/11, seven were native-born U.S. citizens. None of the five foreign-born attackers was a refugee and none was from any of the seven countries listed in President Trump's travel ban. 83 of 94 people who died in those attacks were killed by U.S.-born terrorists (one acting with his Pakistan-born wife).

-- Syrian refugees were subject to the most severe restrictions under Trump's order. But despite that implication that they are a riskier category, not one of the 18,000 Syrian refugees who have been admitted to this country has been implicated in any terror event, lethal or otherwise.

-- Statistics on refugee involvement in lethal and nonlethal post-9/11 terror incidents vary because different analyses use different definitions. But different studies consistently found that very few cases, typically fewer than 20, involved refugees. Of those, a significant number entered the United States as children, or were in the country for many years and were radicalized while living here, so their cases do not indicate that dangerous people slipped through security vetting while being screened for refugee status.

-- A large majority of terrorist acts in the United States were committed by American citizens, more than half of them native-born. A compilation by New America (previously the New America Foundation) found 396 people who were "charged with or died engaging in jihadist terrorism or related activities inside the United States, and Americans accused of such activity abroad." More than two-thirds of those were citizens, 191 U.S.-born and 84 naturalized. Another 46 were legal permanent residents. Other studies showed similar findings.

-- The United States has admitted nearly 800,000 refugees since 9/11. By available evidence perhaps 20 have been involved in terrorism, but not all (those who came as children, e.g.) would have been detected by "extreme" or even perfect vetting. If better screening would have kept out 15 (almost certainly an overestimate), that's one dangerous person for every 50,000-plus legitimate refugees. Extrapolating from that experience, the president's action to lower the 2017 cap on refugee admissions from 110,000 to 50,000 (that's in the executive order, though it has gotten little attention compared to other provisions) will keep out at most one potential terrorist during the year even if the screening process is unchanged, and that one would be statistically unlikely to commit a violent act in the United States.

-- Subjecting large Muslim populations to surveillance and more intense screening has been tried, and has not worked. In 2002-2003 the National Security Entry-Exit Registration System (NSEERS) registered more than 83,000 men from 24 predominantly Muslim countries plus North Korea. More than 13,000 were ordered deported for immigration violations, but as far as can be determined, NSEERS did not lead to any terrorism-related convictions. Six years of spying by the New York Police Department on mosques, Muslim student organizations, and other Muslim targets did not turn up any terrorists either. Similar programs had the same lack of result. Successful terrorism investigations, by contrast, often resulted from tips and cooperation from within the Muslim community.

Compiled by Arnold R. Isaacs, author, From Troubled Lands: Listening to Pakistani Americans and Afghan Americans in Post-9/11 America; online at www.fromtroubledlands.net



Studies analyzing the relation of immigration status to terrorist events in the United States:

"Terrorism in America After 9/11," International Security Program, New America, Washington, D.C. https://www.newamerica.org/in-depth/terrorism-in-america/

Alex Nowrasteh, "Terrorism and Immigration: A Risk Analysis," Cato Institute, Sept. 13, 2016 https://www.cato.org/publications/policy-analysis/terrorism-immigration-risk-analysis

John Mueller, ed., Terrorism Since 9/11: The American Cases (Columbus: Ohio State University, March 2016), http://politicalscience.osu.edu/faculty/jmueller/since.html

Robert Pape et al, "The American face of ISIS: Analysis of ISIS-related terrorism in the US March 2014-August 2016," University of Chicago Project on Security and Threats (CPOST) and Counter-Terrorism Policy Centre, Australian Strategic Policy Institute, Feb. 2017, https://www.aspi.org.au/publications/the-american-face-of-isis-analysis-of-isis-related-terrorism-in-the-us-march-2014august-2016

"By the Numbers: ISIS Cases in the United States, March 1, 2014-January 25, 2016," Center on National Security at Fordham Law, Jan. 25, 2016, http://static1.squarespace.com/static/55dc76f7e4b013c872183fea/t/56a7a90a2399a387c5bc9eeb/1453828362342/ISIS+Cases-+Statistical+Overview+01-25-16.pdf

Lorenzo Vidino and Seamus Hughes, "ISIS in America: from Retweets to Raqqa," Program on Extremism, George Washington University, Dec. 2015,

Charles Kurzman, Triangle Center on Terrorism and Homeland Security, University of North Carolina, annual reports on Muslim-American terrorism suspects and perpetrators, available at http://kurzman.unc.edu/muslim-american-terrorism.

Jens Manuel Krogstad and Jynnah Radford, "Key facts about refugees to the U.S.," Pew Research Center, Jan. 30, 2017, http://www.pewresearch.org/fact-tank/2017/01/30/key-facts-about-refugees-to-the-u-s/

Rights Working Group and Center for Immigrants' Rights at Pennsylvania State University Dickinson School of Law, The NSEERS Effect: A Decade of Racial Profiling, Fear, and Secrecy, May 2012, https://pennstatelaw.psu.edu/_file/clinics/NSEERS_report.pdf

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