Twelve people were killed at the magazine’s Paris office by brothers Said and Cherif Kouachi, who said they were acting on behalf of Al-Qaeda to avenge Charlie Hebdo’s decision to publish cartoons of the Prophet Mohammed.
The killings signalled the start of a deadly wave of Islamist attacks around Europe.
The first trial was held in 2020 with 14 defendants — some tried in their absence — accused of helping the gunmen prepare and organise the attacks in the French capital.
Jail terms ranging from four years to life were handed out for those convicted of helping the gunmen, who attacked the magazine’s office and customers at a Jewish supermarket.
Only two, those given the heaviest sentences, have appealed.
Ali Riza Polat, 37, was sentenced to 30 years in prison after it was ruled he had helped the Kouachi brothers and Amedy Coulibaly secure weapons.
Coulibaly was responsible for the murder of a French policewoman and a hostage-taking at a Hyper Cacher market in which four Jewish men were killed in the same month as the January Charlie Hebdo attack.
Polat’s lawyers have argued that the appeal is a last chance to “correct the mistakes of a judicial system overwhelmed by the scale of these attacks”.
They said he was “wrongly attributed a role he never played” in the attacks.
The other defendant, Amar Ramdani, was handed 20 years in prison for supplying weapons and financing the attacks — the maximum allowed under law.
The Kouachi brothers and Coulibaly were killed during a police assault.
The appeal court will have six weeks to weigh up the degree of responsibility of the pair.
Several days at the start of the trial will be given to hearing testimony from survivors of the attack and relatives of the victims.
Those shot dead in the Charlie Hebdo office included some of France’s most celebrated cartoonists including Jean Cabut, known as Cabu, 76, Georges Wolinski, 80, and Stephane “Charb” Charbonnier, 47.
The Charlie Hebdo killings triggered a global outpouring of solidarity with France under the ‘Je suis Charlie’ slogan.
Later that year, in November 2015, Paris was again attacked when Islamist gunmen went on the rampage at the Bataclan concert hall, the national stadium and at a host of bars and restaurants.