As far as extradition is concerned, in France, people with dual nationality (or several nationalities) are considered to be French and benefit from the rules applicable to French nationals (refusal of extradition). However, the date on which the offence was committed determines whether the perpetrator was French at the time of the offence.
This is the point that poses a problem, as most of the perpetrators applied for Israeli nationality after the fact.
Very few countries extradite their nationals. The question is whether they are prosecuted in their country. Judicial cooperation between France and Israel is very poor. The problem with Israel is that it lets murderers go free.
There are several scandalous cases of refusal to extradite and prosecute (an ex-policeman swatted the father of a rival in a scam buisness, the elderly father died of a heart attack). This has prompted the French state to mount operations with the Italian and Cypriot police to arrest French-Israelis outside of France.
