The September 11 terrorist strikes against the United States have galvanized European intelligence and law enforcement officials into taking a closer look at why Europe has become a haven for groups such as the one that planned and carried out those attacks. They have found that Islamic terrorists, many of them linked to Osama bin Laden and his al-Qaida organization, have taken advantage of Europe's lax border controls. And spotty police and judicial coordination across the continent has given the terrorists a further advantage.

Some of the men who plotted the attacks against the United States lived and studied quietly in Germany for years. They, like the members of other Islamic terrorist cells discovered earlier in Germany and Italy, were able to take advantage of the European Union's open borders to move freely around the continent.

But as security analyst Matthew Dunn, of Control Risk Group in London, points out, those borders became obstacles for police and law enforcement officials, who are trying to detect and catch the terrorists. "There have been lots of reports that people who have come under investigation, say, in France, have just chosen to go to Britain or Sweden or Germany, and have been able to move freely around Europe," he says. "Whereas, in some cases, investigators have been more constrained by restrictions on their own actions, and have had to apply for extradition proceedings, which can take several months or even years to come to fruition."

Criminal justice is a national, and not an EU, responsibility. While there is some cross-border cooperation between police forces and magistrates, it tends to be based on personal relationships. Different laws, different sentencing guidelines and different definitions of offenses hamper cross-border law enforcement efforts. Only six of the 15 EU nations specifically recognize terrorism as a crime. Most countries refuse to extradite their own citizens or hand over foreign nationals charged with an offense that does not correspond precisely to something in their own criminal code.

That is the case of Tarek Maaroufi, a Tunisian-born Belgian citizen identified by Italian magistrates as one of al-Qaida's three top coordinators in Europe. The Italians have issued a warrant for his arrest, because they believe he is a central figure in planning an attack last December on the French city of Strasbourg that was disrupted after a rare example of coordination between French, German and Italian police. But Belgium, which has no legislation specifically targeting terrorism, refuses to extradite one of its own citizens. So Mr. Maaroufi lives freely, though under surveillance, in Brussels.

Islamic terrorist groups like al-Qaida have been on the radar screen of European security services for years. But they were seen as just one threat among many. Analyst Jonathan Stevenson of London's International Institute for Strategic Studies argues that the perception of the threat from these groups was lower in Europe which was more alert to home-grown terrorism, than it was in the United States, until September 11.

"European countries are used to old-style terrorist groups, ethno-nationalist groups and left-wing groups that threaten their security, groups like the IRA, ETA in Spain, and then the groups that were rolled up some years ago in Italy and Germany," he says. "As a result, I think that al-Qaida itself has ... been perceptive enough to see that, given that the perception of the threat is relatively low. Then Europe has been more useful as a staging, logistics and recruitment point, rather than a primary target for terrorist attacks."

But European law enforcement officials say the continent is a target for future attacks. French officials, especially, say there is a new type of Islamic terrorist at large, one that is at home in the West and, therefore, much harder to identify. French officials say two key figures in an aborted plot to blow up the American Embassy in Paris spent time in Britain, where they came under the influence of radical clerics, and then went to Afghanistan for training at an al-Qaida camp.

Although U.S. and British investigators say Britain is not home to an al-Qaida network, French officials insist that, even though Islamic terrorist cells seem to work independently of one another, they actually coordinate their activities in Britain, where radical Islamic groups function openly and in total freedom. But Britain is not alone in adopting what the French call a permissive attitude toward extremist groups.

Such groups have for years tapped into European freedoms, and social benefits, and even public funds, to advance their cause. Experts say they freely engage in propaganda, recruit immigrant youth and intimidate those who oppose them. Sometimes, as in the case of a group based in Cologne, Germany, they preach holy war not just abroad but also at home, inciting violence against the very state that shelters them.

Proposed legal changes in such countries as Britain and Germany are expected to make life tougher for these extremist groups. But Steven Simon, a former U.S. counter-terrorism official under the Clinton administration, says the key is how those laws are used. "Europe has been a very convenient staging, recruitment and logistics base for these terrorists. And whether or not that continues to be the case will depend on how European laws evolve over the next couple of years, and how well law enforcement cooperation develops," he says.

Since September 11, efforts to improve police and judicial cooperation among member states have leapt to the top of the EU's agenda. The Union is moving fast to create a common arrest warrant and step up extradition procedures across the 15 nation bloc. But whether it is moving fast enough to deter terrorist groups from striking again is open to question.