In many countries of Europe, former inmates of the U.S. military prison at Guantanamo Bay, Cuba, have been relishing their freedom. In Spain, Denmark and Britain, recently released detainees have railed in public about their treatment at Guantanamo, winning sympathy from local politicians and newspapers. In Sweden, the government has agreed to help one Guantanamo veteran sue his American captors for damages.

Not so in France, where four prisoners from the U.S. naval base were arrested as soon as they arrived home in July, and haven't been heard from since. Under French law, they could remain locked up for as long as three years while authorities decide whether to put them on trial -- a legal limbo that their attorneys charge is not much different than what they faced at Guantanamo.

Armed with some of the strictest anti-terrorism laws and policies in Europe, the French government has aggressively targeted Islamic radicals and other people deemed a potential terrorist threat. While other Western countries debate the proper balance between security and individual rights, France has experienced scant public dissent over tactics that would be controversial, if not illegal, in the United States and some other countries.

French authorities have expelled a dozen Islamic clerics for allegedly promoting hatred or religious extremism, including a Turkish-born imam who officials said denied that Muslims were involved in the Sept. 11, 2001, attacks on the United States. Since the start of the school year, the government has been enforcing a ban on wearing religious garb in school, a policy aimed largely at preventing Muslim girls from wearing veils.

French counterterrorism officials say their preemptive approach has paid off, enabling them to disrupt plots before they are carried out and to prevent radical cells from forming in the first place. They said tips from informants and close cooperation with other intelligence services led them to thwart planned attacks on the U.S. Embassy in Paris, French tourist sites on Reunion Island in the Indian Ocean and other targets.

"There is a reality today: Under the cover of religion there are individuals in our country preaching extremism and calling for violence," Interior Minister Dominique de Villepin said at a recent meeting of Islamic leaders in Paris. "It is essential to be opposed to it together and by all means."

Thomas M. Sanderson, a terrorism expert with the Center for Strategic and International Studies in Washington, said France has combined its tough law enforcement strategy with a softer diplomatic campaign in the Middle East designed to bolster ties with Islamic countries.

"You do see France making an effort to cast itself as the friendly Western power," as distinct from the United States, he said. "When it comes to counterterrorism operations, France is hard-core. . . . But they are also very cognizant of what public diplomacy is all about."

France has embraced a law enforcement strategy that relies heavily on preemptive arrests, ethnic profiling and an efficient domestic intelligence-gathering network. French anti-terrorism prosecutors and investigators are among the most powerful in Europe, backed by laws that allow them to interrogate suspects for days without interference from defense attorneys.

The nation pursues such policies at a time when France has become well known in the world for criticizing the United States for holding suspected terrorists at Guantanamo without normal judicial protections. French politicians have also loudly protested the U.S. decision to invade Iraq, arguing that it has exacerbated tensions with the Islamic world and has increased the threat of terrorism.

Despite the political discord over Iraq, France's intelligence and counterterrorism officials say they work closely with their American counterparts on terrorism investigations.

With the largest Muslim population in Europe, France is being closely watched in neighboring countries, many of which are tightening their own anti-terror and immigration laws. But even following the Sept. 11 attacks and the March 11 bombings of commuter trains in Madrid, other European countries have been reluctant to fully embrace the French model, part of a legal tradition from the Napoleonic era that has always given prosecutors strong powers.

Britain, for instance, typically takes years to extradite terrorism suspects to other countries and has respected the free-speech rights of imams who praise Osama bin Laden, the al Qaeda leader, and endorse holy war. Until three years ago, Germany did not ban membership in a foreign terrorist organization such as al Qaeda as long as it didn't operate inside the country.

Many of the anti-terror laws and policies in France date to 1986, when the country was grappling with Palestinian and European extremist groups. Since then, the government has modified and expanded those laws several times, gradually giving authorities expanded powers to deport and detain people.

'High Pressure Zones'

Terrorism is "a very new and unprecedented belligerence, a new form of war and we should be flexible in how we fight it," said Jean-Louis Bruguiere, a senior French anti-terrorism judge. "When you have your enemy in your own territory, whether in Europe or in North America, you can't use military forces because it would be inappropriate and contrary to the law. So you have to use new forces, new weapons."

At times, French authorities have pursued terrorism cases outside their borders, taking over investigations from countries unwilling or unable to arrest suspects on their own.

Last year, Christian Ganczarski, a German national and alleged al Qaeda operative, arrived in Saudi Arabia for a religious pilgrimage to Mecca. A Muslim convert who became a personal acquaintance of bin Laden, Ganczarski was suspected by French authorities of helping to organize the April 2002 bombing of a synagogue in Djerba, Tunisia, which killed 21 people.

Saudi officials prepared to deport Ganczarski back to Germany, but when German officials indicated they lacked the evidence to arrest him, Saudi authorities arranged a detour, putting him on a flight with a connection through Paris. When Ganczarski arrived at Charles de Gaulle Airport on June 2, 2003, he was detained for questioning by French police.

Seventeen months later Ganczarski remains in a French jail, under investigation for alleged conspiracy in the Tunisian attack. French investigators have claimed jurisdiction in the case because French nationals were among the casualties in the Tunisia attack.

Also last year, French counterterrorism officials tipped off the Australian government that a visiting French tourist, Willie Brigitte, was allegedly part of a terrorist cell in Sydney that was planning attacks during rugby World Cup events there. Lacking direct evidence of their own, Australian officials deported Brigitte to France in October 2003, where he was arrested. He also remains in jail, where he is subject to regular interrogations.

The French anti-terrorism judge overseeing both cases is Bruguiere, an investigating magistrate who under French law is granted great prosecutorial powers, including the ability to sign search warrants, order wiretaps and interrogate suspects.

Over the past decade, Bruguiere has ordered the arrests of more than 500 people on suspicion of "conspiracy in relation to terrorism," a broad charge that gives him leeway to lock up suspects while he carries out investigations.

"There is no equivalent anywhere else in Europe. This provision is very, very efficient for judicial rule in tackling terrorist support networks," Bruguiere said in an interview. "Fighting terrorism is like the weather. You have high pressure zones and low pressure zones. Countries that have low pressure zones" attract terrorism.

'Erosion of Civil Liberties'

Bruguiere estimated that 90 percent of the defendants he has indicted and brought to trial have been convicted. Critics assert, however, that most people arrested on orders of anti-terrorism judges in France never face terror-related charges and eventually are freed. Official statistics on French terrorism prosecutions are not readily available, so it is difficult to assess the outcome of such cases.

William Bourdon, a Paris attorney representing Nizar Sassi and Mourad Benchellali, two of the four French nationals released from Guantanamo Bay in July, said his clients were rearrested not because they were suspected of any crimes in France, but merely because they had gone to Afghanistan before the U.S.-led invasion in 2001.

Under French law, his clients could remain jailed for up to three years until authorities complete their investigation. "What has been done here is absolutely unfair," he said. "There's a high level of inhumanity in the decision."

Michel Tubiana, a lawyer and president of the Human Rights League in France, told the story of a chicken vendor he once represented to illustrate how easy it is for suspects to be arrested under French anti-terror laws.

He said the vendor, Hakim Mokhfi, was detained in June 2002 after authorities learned he had gone to a camp in Pakistan before Sept. 11, 2001, and knew a person who was an acquaintance of Richard C. Reid, the Briton who pleaded guilty in the United States to charges of trying to blow up an American Airlines flight with explosives concealed in his shoes in December 2001.

On three occasions over the past five months, Tubiana said, outside judges assigned to review the vendor's case have set deadlines for investigating magistrates to either indict or release him. The deadlines have passed, but his client remains locked up, court documents show. "There is in fact no control" over these magistrates, he said. "They are all-powerful."

Tubiana cited a new law enacted last year that drops a requirement for French anti-terror police to have an eyewitness when carrying out a search warrant. The requirement had been intended to prevent the planting of fake evidence.

"There has been a definite erosion of civil liberties in France, and not just with terrorism," Tubiana said. "We're seeing things that would have been unthinkable 10 years ago."

At the same time, Tubiana and other defense attorneys acknowledged that French counterterrorism investigators generally make efficient use of the tools at their disposal.

The Directorate of Surveillance of the Territory, the domestic intelligence agency, employs a large number of Arabic speakers and Muslims to infiltrate radical groups, according to anti-terrorism experts here. Police are also quick to use the threat of preemptive arrest to persuade suspects to work as street informants.

Targeting Clerics

The French government has also stepped up efforts to crack down on radical Islamic clerics. While authorities have long had the right to expel foreigners if they are judged a threat to public safety, lawmakers passed a bill this year that makes it possible to deport noncitizens for inciting "discrimination, hatred or violence" against any group.

The target of the new law: an Algerian-born imam named Abdelkader Bouziane, a cleric living in Lyon who was originally expelled from the country in April after he publicly urged Muslims to attack U.S. targets in France and later told an interviewer that it was permissible for men to engage in polygamy and beat their wives. Bouziane was allowed to return after an appellate court ruled in his favor, but under the modified law was deported last month to Algeria.

Bruno Le Maire, a senior adviser to the interior minister, said authorities have placed about 40 mosques under close surveillance and move quickly whenever they find a cleric preaching radicalism.

"There's not a direct link between what these imams say and terrorism, but there are indirect links that can be dangerous to democracy and the security of our country," he said. "So we have to be very careful with these people."

Other countries, including the United States, have long-standing policies that restrict law enforcement agents from infiltrating places of worship. So far, however, France's aggressive approach has not led to widespread criticism.

Dalil Boubakeur, rector of the Grand Mosque of Paris, said many Muslims support the expulsions and are just as concerned about preventing terrorist attacks as other French citizens. "We find the public arrogance of these extremists completely intolerable," he said. "Fundamentalism is on the rise. . . . This is a real danger. The state should take measures against these types of people that disrupt society, not only when there is a terrorist attack, but before."

Special correspondent Maria Gabriella Bonetti contributed to this report.

In a 2003 anti-terrorism raid near Paris, police escort handcuffed women from the offices of an Iranian opposition group, the People's Mujaheddin.Aymane Sassi reacts to news in July that his brother, Nizar Sassi, and three other detainees freed from the U.S. military prison at Guantanamo Bay, Cuba, would be held in French custody pending the outcome of an investigation.