Attorney Karla Paz said Guatemalan officials rejected a petition for McAfee Thursday without considering the evidence, CNN reported Friday, and Supreme Court action will be sought.
"Due process has been violated. The right to defense has not been respected," Paz said.
Belize wants to extradite McAfee to talk to him about the Nov. 11 shooting death of his neighbor, U.S. businessman Gregory Faull.
McAfee said he fled to Guatemala, where he was arrested for entering the country illegally Wednesday, to escape persecution in Belize.
A spokesman for Guatemalan President Francisco Cuevas said McAfee's asylum request had no basis and was rejected, clearing the way for his extradition to Belize.
ABC News said McAfee, 67, may have suffered a heart attack Thursday before he was found unresponsive in a detention cell.
His legal team initially reported that doctors were treating McAfee for cardiovascular problems but later said he had suffered a nervous breakdown.
Faull was found dead in his beachfront house on an island in Belize shortly after McAfee's dogs were poisoned. Faull had led a neighborhood petition drive against the dogs, describing them as a dangerous nuisance.
McAfee moved to Belize in 2008, 14 years after he sold his interest in McAfee Associates, the computer security firm he founded in 1987.