Would stricter immigration laws have prevented the Tsarnaev brothers' alleged crimes? (FBI)

Sen. Chuck Grassley (R-Iowa) caused a stir Friday by linking the Boston Marathon bombing to the Senate debate over immigration reform.

“While we don’t yet know the immigration status of the people who have terrorized the communities in Massachusetts, when we find out it will help shed light on the weaknesses of our system,” Grassley said. “How can individuals evade authorities and plan such attacks on our soil? How can we beef up security checks on people who wish to enter the U.S.? How do we ensure that people who wish to do us harm are not eligible for benefits under the immigration laws, including this new bill before us?”

Later in the hearing, Grassley conceded, "Evidently, they were here legally."


As Dave Weigel at Slate notes, both of the Tsarnaev brothers, who stand accused of perpetrating last Monday's marathon bombing, were in the United States legally. Dzhokhar, who is currently in police custody after a lengthy manhunt, is a naturalized citizen, while Tamerlan, who died in a shootout with police, had a green card and was applying for citizenship. It was held up because of a domestic violence charge on his record.

That's something of a pattern. Terrorist attacks don't tend to be perpetrated by people who have been denied legal permission to stay in the United  States. The 9/11 hijackers entered the United States through legal channels, albeit in some cases using forged documents. Of the 19 hijackers, only six were found by the 9/11 Commission to have violated immigration law in their stay in the United States. The Commission didn't rule out the possibility that the other 13 may have violated the terms of their visas, but by and large the hijackers were in the country legally.  Another four would-be hijackers were denied visas for a variety of reasons, and as a consequence didn't participate in the plot.

What's more, the best information we have suggests that terrorism doesn't have a whole lot to do with illicit border crossings in general. The National Consortium for the Study of Terrorism and Responses to Terrorism (START) at the University of Maryland put out a report in December detailing 221 border crossings by people later indicted in a federal terrorism-related case. Those crossings were associated with 43 terrorist attacks between 1975 and 2001.

It's possible that the database START uses leaves out some crossings of people who weren't indicted for terrorist acts they committed, so START urges those using its data to exercise caution when comparing that with the total number of U.S. terrorist attacks during that time period. But for the record, there were 1,532 attacks total, of which the border crossing-related attacks make up a measly 2.8 percent. Again, that's a rough low-end figure, but given that the vast majority of attacks in the START database come from the Earth Liberation Front or the Animal Liberation Front, which are predominantly domestic groups, it's likely not too far off.

Of the sample's crossers whose citizenship could be determined, 48 percent were U.S. citizens. Another 18 percent were Canadian citizens. Another 12.6 percent were Irish and another 8.4 percent were British (most of these crossers were involved with the IRA). So of the small percentage of attacks that involved border crossings, it's likely an even smaller percentage are conducted by non-Americans crossing into the United States. A tiny fraction involved either legal or illegal migration by people of Middle Eastern or non-Commonwealth (or in the Irish case ex-Commonwealth) origin.

As a final indication of how unrelated domestic terrorism is from migration issues, take a look at the START database of terrorist events in the United States from 1970 to 2011 (see here, copied from this Guardian database). A mere 15 attacks in that period have produced more than two casualties. Of those, three were part of 9/11: the World Trade Center attacks, the United 93 hijacking and crash and the Pentagon attack.

What about the other 12? Well, there's Columbine; that was done by native-born U.S. citizens. Then there's Oklahoma City; same story. There was the Fort Hood shooting, allegedly committed by Nidal Malik Hasan, a native-born American. There was a bombing at LaGuardia airport that killed 11 people in 1975 and which remains unsolved. There's the Greensboro Massacre, conducted by the Ku Klux Klan and American Nazi Party (all native-born U.S. citizens). There was 1973 spree killer Mark Essex, a native-born American. In 1973, seven people were killed in a Washington, D.C. home owned by Kareem Abdul-Jabaar, allegedly by a group of Black Muslims opposed to a rival group's teachings. The killers appear to have been American-born. Another Black Muslim-related incident left 4 dead at a mosque in Brooklyn.

There was the 1970 Marin County courthouse shooting; Jonathan Jackson, the main perpetrator, was a native-born American. There was the so-called "Alphabet killer" Muharem Kurbegovic, a Yugoslav legal permanent resident who killed three people in a bombing at LAX in 1973. A 1975 bombing by FALN, a Puerto Rican nationalist group, killed four in New York; the perpetrators, as Puerto Ricans, could enter and exit the mainland as they pleased. There was the 2002 LAX shooting (which START lists as having 3 fatalities, while others list 2), which was conducted by Hesham Mohamed Hadayet, an Egyptian national with a green card.

That's twelve. Admittedly, three fatalities is a somewhat arbitrary cutoff, but it's striking that all of the large attacks perpetrated by non-citizens were either conducted by permanent legal residents or by people who entered through legal visa channels. The 9/11 example suggests that further criminal and terror link background checks before the granting of visas may be a worthwhile measure, as would checking for visa overstayers, but nothing in the history of terrorism in the United States suggests that there would be any ill effects to a path to citizenship for undocumented migrants already in the United States.

However, it is worth noting that the alleged Boston bombers entered on asylum, and faced a one-year deadline to apply for a visa. The Gang of 8 immigration bill lifts that deadline. So the bill would have made it slightly easier for the Tsarnaevs to enter the United States. But then again, it also would make it easier for plenty of non-criminals with valid asylum claims to stay in the United States as well.

The original headline stated that both Tsarnaev siblings were U.S. citizens. One is a citizen, the other was a permanent resident. The headline has been changed to reflect this information.