"If we no longer have the right to laugh at terrorists, what arms are citizens left with?" [Editor Philippe] Val asked.
"How is making fun of those who commit terrorist acts throwing oil on the fire?"
A lawyer for the magazine read a letter out from French presidential candidate Nicolas Sarkozy.
Mr Sarkozy noted he was often a target of the magazine but said he would prefer "too many caricatures to an absence of caricature".
But the Muslim groups said Charlie Hebdo's decision to publish the cartoons "was part of a considered plan of provocation aimed against the Islamic community in its most intimate faith".
Feb 7, 2007
French magazine sued for printing Mohammed cartoons
Yes, those cartoons. Charlie Hebdo is being sued by two Muslim groups, Paris Mosque and the Union of Islamic Organisations of France, for insulting people on the basis of religion.