There's a horrible grotesque at work here: the French government's declaration that the 'ultra-gauche' is dangerous and should be weeded out has introduced a new term to public discourse, 'pre-terrorism'. This is particularly terrifying because it allows a certain reshaping of facts: an act of vandalism (recognised as having no possible threat to human life by the police) becomes an act of terrorism because its perpetrator holds beliefs that are displeasing to the state.
Here's the French minister of the interior, Michèle Alliot-Marie on the horrors of the situation: "They have adopted underground methods. They never use mobile telephones, and they live in areas where it is very difficult for the police to gather information without being spotted. They have managed to have, in Tarnac, friendly relations with people who can warn them of the presence of strangers."
Terrible crimes, I'm sure we all agree. I feel any analysis on my part would be superfluous, since there are a couple of nice pieces of work online about the case, from eminent political philosophers Giorgio Agamben and Alberto Toscano: