An immigration judge issued the ruling Monday, The Rochester Democrat and Chronicle reported. Judge John Reid found George Boley, who has been in an immigration detention center in Batavia, N.Y., for two years, recruited children as soldiers and ordered or carried out killings.
Immigration authorities say Boley headed a group called the Liberia Peace Council that was involved in widespread violence. The Liberian Truth and Reconciliation Commission listed Boley as one of seven people who should be tried for war crimes.
Boley denies any wrongdoing. He told the Democrat and Chronicle in 2009 other groups had used his organization's name and had committed the killings he was allegedly responsible for.
His family has been trying to muster support to free him from detention.
He has 30 days to appeal the deportation order and could then ask for a stay while his appeal is heard.
John Morton, head of Immigration and Customs Enforcement, said the case is the first where a judge has used the 2008 Child Soldiers Accountability Act.