I did a little reading about the Tuaregs when I was reading the life of Charles de Foucauld. I think what you want to say is they are Muslim, but they are not Arab. Their version of Islam is in some respects different from the much more numerous Sunni and Shiite Muslims.
The way it was explained to me (and this was verbal by someone who teaches the Guedra etc of the region) was that they are extremely lax Muslims and what they DO do it is done more to appease the hardliners when they are around them.
And they have more way more pagan practices that true muslim. (ie, the Guedra trance).
Granted, this was verbal and I'm running for my notes now ;)