The Southern Poverty Law Center pleaded not guilty Thursday to federal fraud and money laundering charges tied to its use of paid informants within extremist groups, with the organization vowing to aggressively fight the case.

The SPLC was arraigned Thursday afternoon in federal court in Montgomery, Alabama, where federal prosecutors accused the group of improperly using more than $3 million in donor funds to pay informants connected to organizations including the Ku Klux Klan, Aryan Nations affiliates, and individuals who helped organize the 2017 “Unite the Right” rally in Charlottesville, Virginia.