It is worthwhile pointing out that establishing jurisdiction is essential to France, as France won't necessarily be bound by a judgement of the International Court of Justice.
This was the very reason in the "Rainbow Warrior" case (roulishollandis mentioned), of international terrorism committed by agents of the French state in New Zealand, that NZ sought the mediation of the UN Secretary General, and to which France ultimately agreed to the terms negotiated. There was a technical breach of those terms when the two DGSE agents (under house arrest on Hao Island for 3 years) were repatriated to France a year earlier than agreed due to claimed "ill health".
At the end of the day, all law is the result of political action, and the application of International Law is often open to political rejection when an affected state feels offended.