When Attorney General Jeff Sessions was asked how he viewed the car attack in Charlottesville, Va., here's how he responded:

"It does meet the definition of domestic terrorism in our statute," he told ABC's Good Morning America.

That certainly seems to suggest the government is looking into a possible terrorism charge against the suspect, 20-year-old James Alex Fields Jr. At Saturday's rally organized by white supremacists, a car slammed into counterprotesters, killing one and injuring 19.

But according to the Justice Department and legal analysts, it's simply not possible for the government to file charges of domestic terrorism, because no such criminal law exists.

The Patriot Act does define domestic terrorism, and under this designation, the Justice Department has broad powers to investigate, said Neal Katyal, a Georgetown University law professor who served as former President Barack Obama's acting solicitor general and as the national security adviser to the Justice Department.

He said the government has three basic ways to approach the Charlottesville case.

"No. 1, this is a hate crime, under the hate crime statutes," he said. "The second is that this is a conspiracy to deprive individuals of civil rights."

"And the third is, this is an act of domestic terror, which isn't itself a crime," he noted. In short, the government can't file a criminal charge of domestic terrorism, but so defining the incident does allow it to investigate not only an individual suspect, but also any group the suspect may be affiliated with.

In an email to NPR, the Justice Department made the same point.

The commonwealth of Virginia, meanwhile, has charged Fields with second-degree murder and other crimes.

The Charlottesville case has again spurred a discussion about describing far-right violence as terrorism. After the al-Qaida attacks of Sept. 11, 2001, terrorism was associated primarily with radical Islamist groups based abroad.

The State Department has a list of nearly 60 groups, all foreign, that are identified as terrorist organizations. The vast majority are radical Islamists. And the government can charge a person — American or foreign — with terrorism on behalf of these international groups.

Consider this hypothetical: If the Charlottesville attacker emerged from the car and said he was acting on behalf of the Islamic State, he could be charged with international terrorism, according to Katyal.

Inside the U.S., the political debate appears to be shifting, with growing numbers calling for far-right extremism to be identified as terrorism. But that's almost entirely a political discussion, not a legal one.

On the legal front, there's still a good deal of resistance to creating a criminal charge of domestic terrorism.

"It's an incredibly broad label," said Hina Shamsi, director of the national security project at the American Civil Liberties Union. "There's a real danger of the government criminalizing ideology, theology and beliefs rather than focusing on specific criminal acts."

She said creating a domestic terrorism charge could quickly raise all sorts of political questions about free speech and religion. The ACLU opposes any such law, believing it could be politicized and used, for example, against anti-war groups or environmental activists.

Back in 1995, when Timothy McVeigh killed 168 people with a truck bomb at a federal building in Oklahoma City, it was widely described as the worst act of domestic terrorism to that point.

Yet he was charged with, convicted of and executed for killing federal agents and other crimes — but not terrorism.

The government has historically used the term "terrorism" as a general description for a range of violent acts, including those by right-wing extremists, as well as environmental, anti-abortion and far-left groups. But the specific criminal charge is never domestic terrorism.

Another case came to light Monday, when the Justice Department announced it had arrested a man for allegedly attempting to set off a truck bomb in front of a bank in Oklahoma City on Saturday.

The bomb didn't detonate, the department said. But its description of the case is similar to McVeigh's attack, claiming the suspect, Jerry Varnell, 23, was angry with the government.

The FBI's Joint Terrorism Task Force is leading what's being described as a "domestic terrorism investigation." Yet the formal charge against Varnell is "attempting to use explosives to destroy a building in interstate commerce."

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