CLAIRE L. ADIDA is Associate Professor of Political Science at the University of California San Diego. DAVID D. LAITIN is James T. Watkins IV and Elise V. Watkins Professor of Political Science at Stanford University. MARIE-ANNE VALFORT is Associate Professor of Economics at the Paris School of Economics–Paris I Panthéon Sorbonne University.
On January 27, true to his campaign promise  to suspend Muslim immigration, U.S. President Donald Trump signed an executive order restricting all immigration from Iran, Iraq, Libya, Somalia, Sudan, Syria, and Yemen, and indefinitely barring Syrian refugees from entering the United States. By doing so, the Trump administration has taken a definite stance on what it holds as the threat posed by immigrants and refugees to U.S. security. As we argued in April 2016 , however, democracies like the United States “are not opening their doors to terrorism when they let in Muslim immigrants.”
The order’s proponents, echoing Trump’s rhetoric during his presidential campaign, argue that the United States must avoid the kinds of attacks that Europe has suffered in recent years.  But the United States is different from countries like France, where four men posing as Syrian refugees carried out a major attack in November 2015, because those with terrorist intentions from the Middle East cannot slip through American borders as easily. The small number of refugees who are referred by the UN for resettlement  in the United States had already been required to undergo three background checks, three fingerprint screenings, two interviews, and two security checks. Syrian applicants have been subject to additional scrutiny, in a process that usually lasts between 18 and 24 months .
It is therefore no surprise that in recent years, terrorist attacks in the United States have been in decline, despite Trump’s suggestions that the country has failed to keep its citizens safe. According to the Global Terrorism Database , between 2001 and 2008, there were 168 terrorist attacks on U.S. soil, leading to 3,010 deaths, of which 2,996 resulted from the September 11 attacks. Between 2009 and 2015, there were 137 terrorist attacks on U.S. soil, in which 114 people were killed. (Russia experienced 929 terrorist attacks between 2009 and 2015—over six times more than the United States.) Although Trump characterizes his predecessor as weak on national security, the incidence of terror on U.S. soil decreased under former President Barack Obama. Additionally, the two deadliest