"I want an immediate extradition to France," Mourad Hamyd, 20, told an extradition hearing in Sofia, calling his arrest an "injustice... I have been declared a terrorist on the basis of suspicions".
Hamyd was arrested last month in Turkey while allegedly trying to enter Syria to join jihadists. He was handed over to Bulgarian authorities on July 28 and France issued a European arrest warrant.
The warrant, seen by AFP, said that Hamyd, brother-in-law of Cherif Kouachi, was wanted for "conspiracy for preparation of acts of terrorism".
The warrant however makes no mention of Hamyd being suspected of having had any involvement in the attack.
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He was questioned and freed shortly after that attack after being wrongly identified on social media as being one of the three killers.
The warrant says that Hamyd lived with his family in the northern French town of Charleville-Mezieres. In late July, his sister Khadija alerted the French authorities about his "disquieting disappearance".
A search of his computer also found "numerous and recent visits to sites with jihadist content".
The bespectacled Hamyd has three days to change his mind on the extradition. Otherwise the court will issue the extradition order yesterday and he will be handed over within seven days.