So Gary McKinnon, the hacker who cracked the computer systems of the Pentagon and Nasa from his bedroom in north London more than seven years ago, is to be extradited to stand trial in the US. That was the ruling this week of the law lords as they departed on their summer holidays.

They brushed aside the arguments of McKinnon's distinguished legal team that he could not be guaranteed a fair trial there. "The difference between the American system and our own is not perhaps so stark as the appellant's argument suggests," said Lord Brown of Eaton-under-Heywood, in his ruling. "It is difficult to think of anything other than the threat of unlawful action which could fairly be said so to imperil the integrity of the extradition process as to require the accused to be discharged irrespective of the case against him."

Well, who knows what news gets through to Eaton-under-Heywood these days, but if Lord Brown and his four colleagues had done some cursory research on the current state of the US criminal justice system they would know there is a very stark difference between the way he could be treated by the US courts and how he would be treated here.

There may be much wrong with the British criminal justice system but, compared to the lottery that is the American judicial process, there are a number of sober differences. For a start, here you would not find yourself in jail for 50 years for stealing $160 worth of video tapes, or for 25 years for smoking marijuana. Nor does the UK operate a Guantánamo Bay where the most basic legal principles have been abandoned as part of a post-9/11 panic. And there is no guarantee that, if tried in the US, McKinnon would not be confronted by some grandstanding, publicity-seeking judge deeply offended that a chap in a flat in north London can leave a message saying "your security is really crap" on the Pentagon computer, as McKinnon did. After all, one American official in this case has already said that he would like to see him "fry".

Gary McKinnon started his hacking long before the events of September 11 and his offence has nothing to do with terrorism. In fact, much of his exploration was in pursuit of information about UFOs. But, because of the embarrassment he has caused the Pentagon, he is being pursued as if his offence was in some way connected to US national security. He will not, in reality, face 60 years in jail, but he could well receive a grossly disproportionate sentence for an offence that would be dealt with in this country with a fine and community service. Maybe he would have to pay some compensation, although the real financial cost to the Pentagon and Nasa systems is small, certainly nothing like the fanciful, inflated claim of $700,000 being made by the US authorities. The real loss is one of face.

What McKinnon did was expose a faulty security system in a mischievous fashion. Previous hackers in this country who have transgressed in this way, out of curiosity rather than for financial gain, have been rewarded with jobs as security consultants by the very firms whose systems they cracked. McKinnon himself has been congratulated by some members of the US military for showing up the failings of their system. If the US authorities had been smart, they would have invited McKinnon into the embassy and asked him for advice rather than seeking to make him a scapegoat for their own inadequacies.

This week, the law lords had a wonderful opportunity to assert our independence from the US and to make a point about the abandonment of legal principles there since September 11. They have failed to do so. We must now hope that the European court of human rights will step in to prevent a great injustice to a man whose real offence was to tell the Pentagon a blunt truth.