With last week’s approval by Congress of the Bush administration’s legislation on treatment of “terrorism” detainees, the United States has moved into new and deeply disturbing territory.

The debate on torture, which was supposed to be over three centuries ago, has returned to life. Despite superficial disclaimers, the clear intent of the legislation is to make the president the sole authority for determining treatment of detainees, and therefore to allow him to approve interrogation techniques that the rest of the world would stigmatise as torture.

Of course these techniques were being used anyway. But excesses of the executive government in a war or warlike situation are nothing new. What’s new is that the legislature had the opportunity to rein in the executive, and chose not to.

It’s one of those unusually clear moments, when an apparently civilised country does something that the international community regards as beyond the pale. Australia had its own such moment in 2001, when the government chose to tear up the international rule book over Tampa.

Going back further, France shocked the conscience of the world in similar fashion in the Dreyfus affair of the 1890s.

In each case, domestic political considerations blind people to things that outside observers regard as obvious. A program of torture that was conceived and implemented as an emergency response would be one thing. But a program promoted in cold blood as a political tactic is much more shocking.

There are some grounds for optimism. Congressional approval was far from unanimous, with most Democrats opposing aspects of the legislation. One amendment, which would have preserved habeas corpus rights for detainees, was defeated in the Senate by only three votes. And with a Supreme Court challenge to the legislation inevitable, and Democrats now favourites to regain control of Congress next month, it is possible that the effectiveness of the new measures will be shortlived.

After all, the anti-Dreyfusards were comprehensively beaten in the end. But for a time they did enormous harm to France’s reputation. It will take the US a long time to recover from the blow its reputation has just suffered.