Robert Paul Rundo, 34, pleaded guilty in September to one count of conspiracy to violate the federal Anti-Riot Act, the U.S. attorney's office in Los Angeles said.
"Hate and violence are antithetical to American values and tear at our community. It is therefore critical that we protect the civil and constitutional rights of our community against those who promote divisiveness," U.S. Attorney Martin Estrada said in a statement.
4 alleged SoCal white supremacists indicted for political rally violence
Rundo's attorney didn't immediately respond to an email seeking comment.
Prosecutors say Rundo co-founded the Rise Above Movement, which they describe as "a combat-ready, militant group of a new nationalist white supremacy and identity movement." He and two others were accused of planning and engaging in violence at gatherings in Huntington Beach, Berkeley and San Bernardino in 2017.
Rundo was arrested in 2018 for inciting violence at California protests and at a deadly riot in Charlottesville, Virginia. A federal court dismissed the charges in 2019, but they were reinstated by a federal appeals court in 2021.
Rundo had left the United States after the charges were dismissed and was extradited last year from Romania when they were reinstated.