The time has come for the trial of the traitor Ganelon. Charles assembles a council of his lords and barons to serve as a sort of jury, to decide the criminal's fate. Ganelon is brought forth in chains. Charles argues that Ganelon has betrayed the twelve peers. The argument that develops is not about the facts of the case, but their meaning. Ganelon does not dispute that he planned with the pagans the massacre at Roncesvals, but he defends himself by arguing that this was not treason, that he was only taking his just revenge: "Since Roland took my gold and property, I therefore planned his suffering and death; but I'll concede to no one this was treason" (272.3758-3760.) Ganelon tells the assembled barons how Roland had picked him to be an envoy to Marsilla because of his grudge against his stepfather. He recounts how he then offered an open challenge to Roland and his comrades and argues that this makes his action revenge, not treason. Ganelon's friend Pinabel says that if any of the barons ask that Ganelon be hanged, he will prove him wrong in trial by combat, and show that he lies by beating him in a duel.
The barons debate this question of justice. Because no sentence they can pass will bring back Roland, and because Ganelon is a well-respected and well-born man who could still be useful to Charlemagne, the men decide to let him live. The one dissenter is Thierry.
When the barons announce their verdict to Charlemagne, he is deeply disappointed. Thierry then speaks up, arguing that, while Roland may have wronged Ganelon, Ganelon betrayed Charlemagne by attacking a man in Charlemagne's service. Thus, says Thierry, Ganelon should die.
Now Thierry and Pinabel must fight. Pinabel states, "I say [Thierry] lies and will contest it with him" (278.3844). Each combatant must have a guarantee; thirty of Pinabel's relatives offer themselves as surety for him, and Charlemagne offers himself for Thierry. Pinabel and Thierry offer up their right-hand gloves to the emperor, and a formal battle is arranged. The fighters make their confessions, arm themselves, and mount their horses, while everyone gathers around to watch.
The two knights soon unhorse each other and begin to fight standing, with their swords. Pinabel is the stronger man, and wounds Thierry badly, but the Lord does not want Thierry to die. God works a miracle; Thierry slashes open Pinabel's skull. Thus the Franks see that Ganelon is a traitor. For good measure, they decide to hang all thirty of Pinabel's relatives too. Ganelon, however, needs a more painful death; each of his limbs is tied to a wild horse, and he is literally torn apart. The traitor goes to his damnation.
The trial-by-combat which is used to decide the argument between Ganelon's supporter Pinabel and Charlemagne's supporter Thierry vividly brings before us the medieval conception of the justice of God. Pinabel supports Ganelon's case that his organization of the Saracen rear guard was an example of justified and openly proclaimedthus validrevenge on Roland and his cronies, the twelve peers of France. Thierry argues that, since Roland was at the time serving Charlemagne, Roland should have enjoyed immunity from such attacks for the duration of his service, and Ganelon's action was thus a betrayal of Charlemagne. To determine who is right, Pinabel and Thierry fight, so that God can reveal which man is just by intervening and making him the victor. This, in a microcosm, is the same view of battle that motivates Charlemagne's campaign in Spain; the cry of Thierry"Today let God show which of us is right!"could be the general cry of the Franks in Spain (283.3898). To make it clear that it is the good man, and not merely the stronger, who wins, and to show that God really does intervene, the poet emphasizes that Pinabel is much stronger than Thierry. Thus we can better enjoy the sureness of the justice of such a trial.