Last week, Dylann Roof was charged with 33 criminal acts, including hate crimes and firearm violations, for his killing spree at a historic African American church in Charleston, South Carolina. Even before the charges were announced, questions were raised about FBI Director James Comey’s reluctance to call the attack an act of domestic terrorism, especially since his office is quick to label acts of violence by Muslims terrorism.

The discrepancy in the way authorities handle mass shootings by different actors reflects distinctions that are baked into the criminal code. At the end of the day, Roof’s alleged crimes didn’t align with any that would qualify as terrorism.

Federal law defines domestic terrorism roughly as violent acts occurring within the United States “intended to intimidate or coerce a civilian population” or to influence government policy or conduct. But whether or not a violent crime satisfies this definition doesn’t necessarily bear on the criminal charges brought by federal prosecutors. As Attorney General Loretta Lynch noted when announcing the charges against Roof, there is no singular crime of domestic terrorism encompassing acts of politically motivated violence. Instead, federal law specifies a wide array of crimes as terrorism-related offenses, regardless of intent, including hijacking an airplane, assassinating a government official, detonating certain kinds of explosives or chemical weapons, or bombing a government facility.

This structure allows prosecutors to seek high terrorism penalties while avoiding the problems of proving that the perpetrators actually have the motives characteristic of terrorism. More common offenses like shootings or kidnappings don’t necessarily fit into this scheme for obvious reasons: including them would sweep in regular criminal activity.

Such criminal offenses can be charged as terrorism if there is some kind of international connection. Violence transcending national boundaries or directed against Americans overseas may meet specific statutory prohibitions against terrorism-related activity. 

By far the most common terrorism-related charge is material support for terrorism, which doesn’t necessarily involve any violent activity, but does carry the heavy penalties typically associated with terrorism. According to NYU’s Center for Law and Security, in 2011, 87.5 percent of terrorism prosecutions were for material support (a sharp rise from 11.6 percent as recently as 2007). Federal law includes two flavors of material support:

1) Title 18 US Code 2339A, which prohibits providing material support for any one of a set of enumerated terrorism-related offenses; and

2) Title 18 US Code 2339B, which prohibits providing material support to a designated foreign terrorist organization.

Material support includes property, services, training, expert advice or assistance, personnel (including the person charged), and transport.

Extending the material support framework to cover Roof’s alleged activities, particularly section 2339B, would open a Pandora’s box of problems. The charge depends on identifying particular terrorist organizations that are banned from receiving support. If extended to domestic groups, the political aspect of such a designation (already fraught in the international context) would carry enormous First Amendment risks. Because terrorism is inherently a political crime, extending material support would allow the government to assign the label to groups with unpopular beliefs. Provided the opportunity, former FBI Director J. Edgar Hoover would no doubt have been delighted to designate as terrorist the civil rights groups and anti-war protesters he so detested. Nor is this solely a historical problem: as recently as 2008, the Bureau classified environmental and animal rights advocacy groups as the biggest domestic terror threat.

The risk of abuse is particularly acute because material support laws don’t just cover people who carry out (or even deliberately support) violence. In its controversial decision in Holder v. Humanitarian Law Project, the Supreme Court held that even providing a terrorist group with training in how to peacefully resolve conflicts could qualify as material support. As cases such as the prosecution of the Holy Land Foundation charity show, the intent requirement for material support can be interpreted broadly. After a mistrial, the defendants in that case were convicted for donating money to legitimate religious charities in Palestine that were allegedly affiliated with Hamas. At trial, the government conceded the charities (which were not themselves designated as foreign terrorist organizations) had no financial link with Hamas. Rather, prosecutors won convictions by arguing that contributing to charities that operated in Hamas-controlled territory effectively provided material support to the group by strengthening its standing in the community. Material support laws have also been used to criminalize what seems like pure speech. Tarek Mehanna was convicted of material support based on evidence that he viewed, translated and disseminated al Qaeda propaganda on his own volition. The prosecution never established that Mehanna had been in contact with al Qaeda, let alone that he received instructions from them. In sum, given their expansive reach and history of overbroad application, material support laws are hardly a solution for addressing domestic terrorism issues.

Given this framework, it’s no surprise that the Department of Justice didn’t charge Roof with terrorism. Rather, DOJ chose to go down the hate crimes route. Federal law criminalizes violence perpetrated as a hate crime, defined as any attempt to cause bodily injury to a person “through the use of fire, a firearm, a dangerous weapon, or an explosive or incendiary device” because of that person’s actual or perceived race, color, religion, national origin, ethnicity, gender, disability, or sexual orientation. Where a hate crime results in death, the maximum sentence is life in prison.

While these legal standards help explain prosecutors’ charging decisions in Roof’s case, they don’t address the societal importance of how we describe violence, raised in this Just Security post. After the Charleston attack, some in the press and government were cautious about attaching the terrorism label to a Muslim man’s shooting of military personnel in Chattanooga, which took place just weeks later. In bringing federal hate crimes charges, the Department of Justice recognized the racial animus that allegedly motivated Roof. The Attorney General went so far as to call hate crimes “the original terrorism.” But, unlike in terrorism prosecutions of Muslims where the least interest in Al Qaeda or ISIS is enough to brand an act part of a global threat, there was no attempt to place Roof’s crime in the context of the right wing threat that state and local law enforcement officials have identified as the biggest terrorism risk in their communities. This differential treatment was neatly captured on Twitter in the wake of yet another shooting, in a movie theatre in Louisiana: #lonewhitemale.