Mohamed Mahamud, Abdelkader Osman Ali and Mahamud Abdi Mohamed were convicted on priacy charges and sentenced Friday, Radio France Internationale reported.
During their trial, the defendants alleged that extreme poverty forced them to turn to piracy.
Arnaud Colon de Franciosi, a lawyer for the survivors of the attack, said his clients aren't out "for vengeance" but said the accused should be held responsible.
Colon de Franciosi also blamed the French government for carrying out an operation that was intended to frighten potential pirates and did not pay enough attention to the hostages' safety, leading to the death of Florent Lemacon.
"I believe that Florent Lemaçon died for reasons of state," Colon de Franciosi. "This operation was meant as a powerful signal to the Somalis, the hostages were a secondary consideration."