A prominent Alabama non-profit at the forefront of efforts to name-and-shame what it calls right-wing extremists in America, the Southern Poverty Law Center, finds itself under the microscope after one of its staff attorneys was arrested and charged with domestic terrorism during an Atlanta protest Sunday night.

Thomas Jurgens was among 34 people arrested — 23 of whom were subsequently charged — after black-clad protesters hurled rocks and Molotov cocktails at police officers and equipment at a police training facility under construction outside Atlanta that protesters have come to call “Cop City.” Like Mr. Jurgens, most of those charged were from outside Georgia, including two foreign nationals from Canada and France.

Atlanta’s police chief, Darin Schierbaum, called the incident a coordinated attack. “This was a very violent attack, very violent attack,” he said. “This wasn’t about a public safety training center. This was about anarchy.” Georgia’s governor, Brian Kemp, said Monday that the people involved “chose destruction and vandalism over legitimate protest, yet again demonstrating the radical intent behind their actions.”

Police offered no further details on what exactly Mr. Jurgens is accused of doing during the protest, but his employer said he was at the Atlanta Public Safety Training Center as a legal observer under the auspices of the National Lawyers Guild. The non-profit called his arrest an example of “heavy-handed law enforcement intervention against protesters.”

“This is part of a months-long escalation of policing tactics against protesters and observers who oppose the destruction of the Weelaunee Forest to build a police training facility,” the center said. “The SPLC has and will continue to urge de-escalation of violence and police use of force against Black, Brown and Indigenous communities — working in partnership with these communities to dismantle white supremacy, strengthen intersectional movements and advance the human rights of all people.”

The Southern Poverty Law Center, founded in 1971 and based at Montgomery, Alabama, began as a civil rights organization focused on mounting legal campaigns and compiling dossiers on the Ku Klux Klan across the United States. Beginning in the mid-1980s, the group expanded its tracking efforts beyond white supremacist groups to what it called “right-wing extremism” in the country.

In the years since that transition, the center has come under increasing criticism from conservatives in America who say it demonizes legitimate right-of-center political debate in the interest of furthering its liberal agenda and growing its donor base. It has labeled such groups as the Federation for American Immigration Reform and the American Family Association as “SPLC designated hate groups.”

Most recently, the center came under fire after an FBI field office report was leaked that warned of a growing domestic threat from “violent extremists in radical traditionalist Catholic ideology.” These radical Catholics, the FBI report stated, frequently embrace “anti-Semitic, anti-immigrant, anti-LGBTQ, and white supremacist ideology.” The FBI, which later recanted the report, cited publications from the Southern Poverty Law Center as evidence of the threat.