The war on terror, which we were once told was infinite, seems past its sell-by-date. Even David Miliband has declared the term to be "misleading and mistaken". But its effects on our polities persist. Following an age-old script, laws that had been sold as emergency measures have sunk their roots deep into the practices and mentalities of our governments. All forms of dissent that are linked, however tenuously, to politically-motivated illegal behaviour now fall within the purview of anti-terrorism measures, which claim to a nebulous "security" as their ultimate rationale.

While the geopolitical imperatives that underlay the war on terror are being fundamentally questioned, anti-terrorism continues to be used and abused as a flexible repressive instrument across Europe and beyond. From ecological activism to sociological research, there is little that anti-terrorism legislation cannot cover. The case of the "Tarnac Nine", which has recently drawn such attention in France after a series of spectacular arrests on 11 November 2008, is a case in point.

Named after the village in the Corrèze district where a number of the prosecuted lived collectively and ran a grocery store and film club, the case revolves around the accusation that these politicised 20- and 30-somethings were responsible for a series of sabotage actions against the high-speed TGV trainlines in early November, which resulted in massive delays. From the outset, the case has been choreographed by the government, specifically by Sarkozy's minister of the interior, Michèle Alliot-Marie.

To consider the Tarnac case is to be faced with a pattern for the criminalisation of dissent which is becoming ever more general, and which is likely to intensify as Europe (witness the recent events in Greece) is confronted with forms of social conflict which challenge the viability of the socio-economic order.

The French authorities have made it clear that the aim of this highly spectacular operation was to send a pre-emptive message, to nip in the bud the perceived threat of anti-capitalist movements that refuse the parliamentary arena and opt for direct action. This is what the French security services, with the imprecision typical of inquisitions, have been referring to as the "anarcho-autonomist tendency". They have also referred to these political milieus as "pre-terrorist".

The term is key. To the extent that terrorism is no longer perceived as a tactic, however repugnant, but as a kind of total crime beyond the pale of explanation or negotiation, the "pre-terrorist" is already on the way to becoming an absolute enemy of the state. This is how the same material act – the sabotage of a train line, for instance – may be perceived as an act of vandalism in one case, and as a political threat to the state in another. The consequences are clear, and they are disturbing.

The implementation of antiterrorist legislation is profoundly arbitrary and selective, hinging on the political proclivities of ministers, magistrates and the police, increasingly acting in concert and bypassing customary legal safeguards, above all the presumption of innocence. If hard evidence is absent – as it seems to be in the Tarnac case – then lifestyle and beliefs will do.

This was the approach taken by the minister of the interior herself. Recognising that there was no sign of attacks against persons in the whole affair, she nevertheless declared: "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 the village of Tarnac, friendly relations with people who can warn them of the presence of strangers." The very fact of collective living, of rejecting an astoundingly restrictive notion of normality (using a mobile, living in cities, being easily observable by the police) has itself become incriminating.

The prosecution's other plank, the alleged authorship by Julien Coupat (the only one of the accused still under preventive incarceration) of an anonymous book entitled The Coming Insurrection, which refers to acts of transport sabotage as part of an anti-capitalist rising of "communes", also follows the pattern where the "pre" in pre-terrorism is defined by political statements or beliefs at odds with the current order.

The support committee of the Tarnac Nine has lucidly argued that antiterrorism has become a full-fledged method of government, a wilfully vague expedient in the arsenal of the modern state. There is much at stake. We are losing the political literacy, and the legal capacity, to distinguish between sabotage and terrorism, vandalism and mass murder, as every oppositional alternative to the status quo is swallowed up under the umbrella of terrorism. In times of crisis and possible turmoil, this one-dimensional thinking is profoundly dangerous, and an insidious threat to everyone's "security".