This article belongs to the debate » 9/11, Menschenwürde und die liberalen Grundwerte
30 März 2022

Does the Threat of Terrorism Justify Migration Restrictions?

Since the beginning of the War on Terror in 2001, and especially since the rise of ISIS and the Syrian Civil War, beginning in 2011, Western nations have adopted various policies barring migrants and refugees based on fear of terrorism and other security threats. These range from US President Donald Trump’s anti-Muslim travel bans to restrictions adopted by various European countries in the wake of the Syrian refugee crisis of 2015.

As I write these words in March 2022, European nations have adopted a much more open attitude towards refugees fleeing Russia’s brutal invasion of Ukraine. But a similar anti-migrant backlash could potentially occur in this case, as well, especially if the crisis goes on for a long time.

In both Europe and the United States, fears of terrorism and violence have been exploited by anti-immigrant nationalist political movements. They were a key theme of Donald Trump’s campaign in 2016, and also repeatedly used by European nationalist movements, such as the AfD in Germany, the National Front in France, and Viktor Orban’s nationalist government in Hungary, among others. Such tropes were even used in countries like Poland and Hungary, where the number of Muslim and Middle Eastern migrants was very low.

Concerns about terrorism are, to some extent, understandable. But the actual risk of terrorism caused by migrants is extremely low. And that risk can be mitigated by methods other than barring large numbers of refugees fleeing horrific violence and oppression. Indeed, accepting such refugees can actually help combat terrorism more than further it. It can also help reduce other security risks. Barring migrants for the sake of achieving marginal reductions of already very low risks might be justified if restrictions imposed few or no morally significant costs. But, in fact, barring migrants fleeing oppression and war is a grave wrong. It inflicts enormous harm, violates human rights against unjust discrimination, and is also inimical to concepts of dignity prominent in modern European and international law jurisprudence.

The Risk of Terrorism by Migrants is Low

The risks of terrorism by migrants are low and can potentially be mitigated further by “keyhole” solutions that address the problem by means less draconian than the complete exclusion of migrants.

The risk that an American will be killed by an immigrant terrorist in a given year is so infinitesimal that it is actually several times lower than the risk that he or she will be killed by a lightning strike during the same timeframe.1) Over a 40 year period, the number of Americans killed by terrorist entrants from any of the five majority-Muslim countries covered by Donald Trump’s 2017 “travel ban” order was zero. The risk in European countries was comparably low,2) also in the same general ballpark as common everyday dangers. Even if these risks were to increase several-fold as a result of expanded immigration, they would still be extremely small.

Whether immigration increases the risk of terrorism at the margin at all is actually disputed by experts. Some studies find no effect on terrorism rates, even when migration increases from Muslim-majority nations and countries that themselves have terrorism problems.3) Others conclude that while immigration generally does not increase terrorism, increased migration from nations with high terrorism rates can also modestly increase the risk in the destination country.4) An analysis of European data from 1980 to 2004 concludes that increased immigration does not result in increased terrorism rates caused by the immigrants themselves, but does lead to an increase in terrorism by domestic right-wing terrorists hostile to migrants.5)

If this last finding is sound, it suggests a pathway by which immigration does indeed significantly increase terrorism. But it would be perverse to restrict migration for the purpose of limiting terrorist attacks generated by right-wing nativists. It would also set a dangerous precedent. By yielding to terrorist demands, it could incentivize more terrorism by other groups seeking to influence public policy. If the tactic is proven effective for right-wing nationalists, left-wing radicals, radical Islamists, and others would be encouraged to adopt it, as well. Historically, successful tactics pioneered by one set of violent extremists are often imitated by others.

There are some ways in which migration restrictions can actually increase terrorism risks  and undermine efforts to combat terrorist organizations. First, they may feed into the propaganda of terrorist groups, claiming that the West is hostile to Muslims, Arabs, or other groups targeted for migration restrictions. Second, allowing migrants from areas controlled by terrorist groups or hostile anti-Western regimes to come to the West reduces the amount of people and resources under those entities’ control, thereby weakening them. Finally, social science evidence suggests that having a large Diaspora in liberal democratic societies can help promote liberalization in the migrants’ home countries, thereby potentially weakening the grip of oppressive anti-Western rulers. One mechanism for such effects is the spread of liberal ideas from migrants to their friends and relatives who remain in their countries of origin. These are among the reasons why ISIS hailed Trump’s 2017 travel ban as a “blessed ban.” If your supposed effort to fight terrorism is praised by the terrorists themselves, it may be time to reconsider.

Why Terrorism-Based Migration Restrictions Cause Harm

Even if migration increases terrorism risks only slightly, it might be argued that is still enough to justify restricting it, at least in the case of migrants from nations that may seem to pose relatively higher risks. After all, even one terrorist attack is one too many. But this analysis implicitly assumes that migration restrictions have few or no costs, or at least none that destination country governments are obliged to consider.

In reality, barring migration has enormous costs, for both migrants and destination countries. The cost to the former is obvious. Barring or severely restricting migration from nations with repressive governments and powerful terrorist movements inevitably consigns hundreds of thousands of people to lives of oppression and poverty, and sometimes even to death.

There are also large costs to destination countries. Among other things, immigrants – including those from poor and oppressed nations – make disproportionate contributions to scientific innovation, and are also disproportionately likely to become entrepreneurs. To take just one dramatic recent example: the developers of the first two successful Covid-19 vaccines approved by the US government were immigrants or children of immigrants from majority-Muslim nations – precisely the sorts of countries Western nativists advocate targeting for migration restrictions. Had these individuals or their parents been forced to remain their countries of origin, it is likely vaccines would have taken longer to develop, and hundreds of thousands more people would have died in the pandemic – vastly more than have ever been killed by migrant terrorists.

Statistically, it is likely that at least a few the migrants barred by terrorism-inspired migration restrictions would have also made major scientific or other innovations if given the chance. Even one or two such lost opportunities could easily outweigh any acts of terrorism prevented by the restrictions many times over. And, obviously, even less exalted migrants who merely do ordinary jobs also make important contributions to our economies. Economists estimate that the elimination of migration restrictions throughout the world would roughly double the world’s GDP. That’s a staggering amount of new wealth that would benefit natives of receiving countries, as well as immigrants.

America and European citizens also suffer from the negative civil-liberties effects of immigration restrictions, such as increased racial profiling used by enforcement agencies (which necessarily impacts citizens who belong to the same racial or ethnic groups as illegal migrants, or even just look like they do). In thousands of cases, US authorities have even mistakenly detained or deported citizens whom they mistook for illegal migrants.

The Injustice of Migration Restrictions

Restricting migration to prevent small increases in terrorism is also unjust for reasons that go beyond consequentialist considerations. Imagine that migrants from Nation A have higher terrorism rates than natives Nation B, but the vast majority of residents of both are not terrorists. Perhaps 1 in 100,000 migrants from A is a terrorist, which is true of only 1 in 1 million residents of B – a ten-fold difference vastly greater than what we observe in real life! Still, barring all or most migration from A into B means imposing severe restrictions on the liberty of many thousands of people merely because they happened to be born to the wrong parents, in the wrong place.

We readily see the injustice of such measures in the domestic context. I live in the state of Virginia, which borders on West Virginia, a significantly poorer state with a much higher crime rate than our own. But virtually everyone agrees that it would be unjust to bar migration from West Virginia to Virginia, merely because migrants from the former may be more likely to commit violent crimes than native-born residents of the latter.

Similarly, in the US, young black males, on average, have higher crime rates than members of many other ethnic groups. White males, in turn, are disproportionately likely to become domestic terrorists. Native-born whites  were also disproportionately represented among those who attacked the Capitol on January 6, 2021, in an attempt to overturn the results of the 2020 elections. It does not follow, however, that we would be justified in imposing severe restrictions on the freedom of movement of either black males or white males as a group. In both cases, it would be deeply unjust to restrict the freedom of large numbers of people merely because they happen to be members of the same racial or ethnic group as others who have committed various crimes and misdeeds. The same point applies to potential immigrant groups singled out for exclusion merely because others born in the same place have a disproportionate propensity to commit acts of terrorism.

Such discrimination on the basis of ethnicity or national origin stands also in tension with European and international law rights to “human dignity.” Theories of dignity take many different forms. But none of them are easy to square with consigning large numbers of people to lives of poverty or oppression simply because they come from the same region or the same ethnic group as a small number of terrorists.

If differences in crime rates or terrorism rates do not justify racial, ethnic, or regional restrictions on domestic freedom of movement, the same point applies to international migration. There is nothing morally special about international borders, that justifies discrimination on the basis of morally irrelevant characteristics such as parentage or place of birth. And that is especially true when – as is often the case – the discrimination is in part motivated by racial, ethnic, or religious bigotry.

In Chapter 5 of my book Free to Move: Foot Voting, Migration, and Political Freedom, and other writings, I respond in greater detail to clams that migration restrictions can be justified on the grounds that particular racial or ethnic groups are the true owners of given territories, and therefore have a right to exclude members of other groups. I also address arguments that national governments have a right to exclude because their rights analogous to those of owners of private homes or members of a club. Here, I will merely mention that such arguments, if applied consistently, have dire implications for natives, as well as migrants. If the majority ethnic group of France has a right to exclude non-French people, why not the majority ethnic group of the province of Quebec, the state of Texas, or Scotland? Perhaps Quebecers should be allowed to bar Anglophone Canadians, and Scots to bar the English. And if national governments are truly analogous to homeowners or club members, it follows that they can restrict the speech, religion, and liberties of their citizens, much as a homeowner can restrict the range of views expressed and religions practiced in her house.

The case for terrorism-based immigration restrictions is further weakened by the availability of alternative ways to reduce the danger. Because terrorism risks from migration are already so low, it may be very difficult to reduce them still further. However, tapping the vast new wealth created by immigration can potentially pay for extensive new security and counterterrorism operations, if necessary. In Chapter 6 of Free to Move, I describe how shifting the resources currently devoted to enforcing American immigration restrictions could easily pay for many thousands of additional police officers. Social science research indicates that increasing the number of cops on the streets can significantly reduce violent and property crime, whether perpetrated by immigrants or natives, thereby greatly improving public safety. Such increases can also be coupled with measures to reduce police abuses and racial profiling. If necessary, we can also use some of the funds saved on immigration enforcement and wealth generated by increased migration to finance additional counter-terrorism operations.

None of the points made above prove that terrorism threats can never justify immigration restrictions. Imaginative academics and others can always come up with hypothetical scenarios where immigration restrictions are the only way to prevent massive atrocities by terrorists. But it does suggest there should be a strong presumption against such restrictions, based on both consequentialist and intrinsic moral considerations.

Ilya Somin is Professor of Law at George Mason University, and author of Free to Move: Foot Voting, Migration and Political Freedom, from which parts of this post are adapted.


1 According to the National Weather Service, an average of thirty-one Americans were killed by lightning each year, from 2006 to 2015. National Weather Service, “How Dangerous Is Lightning?,” available at By contrast, the annual incidence of death by immigrant terrorists is far lower. See Alex Nowrasteh, “Terrorism and Immigration: A Risk Analysis, Cato Institute Policy Analysis No. 758 (Dec. 13, 2016), available at
2 See Alex Nowrasteh, “Fatalities and the Annual Chance of Being Murdered in a European Terrorist Attack,” Cato Institute, June 21, 2017, available at
3 See, e.g., Andrew C. Forrester, Benjamin Powell, Alex Nowrasteh, and Michelangelo Landgrave, “Do Immigrants Import Terrorism,” Cato Institute Working Paper No. 56, July 31, 2019, available at; Axel Dreher, Martin Gassebner, and Paul Schaudt, “The Effect of Migration on Terror: Made at Home or Imported from Abroad?” CESifo Working Paper Series No. 6441 (2017), available at
4 See, e.g., Vincent Bove and Tobias Bohmelt, “Does Immigration Induce Terrorism?,” Journal of Politics 78 (2016): 572–88.
5 Richard J. McAlexander, “How Are Immigration and Terrorism Related? An Analysis of Right- and Left-Wing Terrorism in Western Europe, 1980–2004,” Journal of Global Security Studies 1 (2019): 1–17.

SUGGESTED CITATION  Somin, Ilya: Does the Threat of Terrorism Justify Migration Restrictions?, VerfBlog, 2022/3/30,, DOI: 10.17176/20220330-131119-0.

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