The Colombian Supreme Court has authorised the extradition of two top paramilitary leaders and a guerrilla commander to the United States.
Palmera is the most senior Farc rebel in captivity
Only one of the men, who are accused of drugs trafficking and money laundering, is in custody.
The court ruled that the extradition request complied with Colombian law.
Right-wing paramilitaries and left-wing guerrillas are bitter enemies, but now have a common cause, with drug traffickers, against extradition.
The wanted men are Carlos Castano, Salvatore Mancuso and Ricardo Palmera, better known by his guerrilla alias, Simon Trinidad.
Castano was the founder of the right wing paramilitary army, the United Self-Defence Forces of Colombia, the AUC. His whereabouts are unknown and some people believe he is dead, murdered by rival factions.
His successor, Salvatore Mancuso, is currently the chief negotiator in peace talks with the government.
Mancuso was allowed to address Colombia's Congress in July
The authorisation of his extradition will put further pressure on the Colombian government to refuse him amnesty for his crimes and could endanger sensitive peace negotiations, says the BBC's Jeremy McDermott in Bogota.
Simon Trinidad is the most senior guerrilla of the Farc, the Revolutionary Armed Forces of Colombia, and he is currently in captivity.
There have long been alliances between drugs traffickers and the warring factions and now for the first time there is evidence of non-aggression pacts in certain parts of the country between paramilitaries and guerrillas.
Should the peace process with the paramilitaries fail, and the state continue to pursue them, they may opt to put aside their differences with the guerrillas and unite against extradition, our correspondent says.