i read its a 7 years commitment, they give you french citizenship, a new identity (if wanted) and a pardon of all crimes with a guarentee of no extradition.
They stole the idea from Islam.
The idea that the Legion is home to a lot of hardened criminals is dated. Every recruit's finger prints are checked through INTERPOL. I'm sure they don't care about the odd DWI or criminal non-support warrant, but serial killers will find themselves in a French jail post haste.