In terms of Islamic extremists in Canada [as] they regard the proximity of Canada to the U.S., it's making Canada a kind of Islamic extremist aircraft carrier for the launching of major assaults against the U.S. mainland.

--David Harris, former chief of strategic planning for the Canadian Security Intelligence Service

The above, slightly overdramatic statement is taken from an interview with Frontline all the way back in May 2001. Just last week, the United States finally got around to instituting identification checks on its sparsely patrolled 5,500-mile northern border. These replace the longstanding honor system beloved of frequent border crossers and aspiring terrorists alike.

As of January 31, U.S. and Canadian citizens age 20 and up must present proof of citizenship and identity to enter the country. The simple oral declaration that one is an American or Canadian citizen will no longer suffice.

U.S. Customs and Border Protection (CBP), a service of the Department of Homeland Security, has its work cut out for it. In just three months last year, from October to December, CBP officers reported 1,517 instances of individuals stopped at the border falsely claiming to be U.S. citizens. And according to a report from the Government Accountability Office dated September 2007, investigators were able "to cross undetected, successfully simulating the cross-border movement of radioactive materials."

The threat is not merely hypothetical. Not only have members of extremist groups and wanted suspects found a congenial haven in Canada, they have done so at a time when immigration to Canada from terror-exporting regions is on the rise.

The list of terrorist attacks planned or perpetrated by Canada-based individuals--of which the "millennium plot" against Los Angeles International Airport is only the most famous--is already considerable. The millennium plot, of course, was foiled when an alert border guard at Port Angeles, Washington, arrested an Algerian resident of Canada attempting to enter the United States with nitroglycerin and four timing devices concealed in a spare-tire well of his car. A member of the Algerian Armed Islamic Group, Ahmed Ressam is serving 22 years in prison.

More recently, on January 18, a New York judge sentenced Canadian Mohammed Jabarah to life for plotting to blow up the U.S. embassies in Manila and Singapore in 2001; apparently his clean Canadian passport helped him become an al Qaeda operative. The October 2002 bombing of a night club in Bali and a 1996 truck bomb attack in Colombo, capital of Sri Lanka, also had Canadian connections.

According to Le Figaro, Canadian authorities recently confirmed that a Lebanese Palestinian sought by France for his role in the 1980 bombing of the Rue Copernic synagogue, which killed 4 and injured 20, is in Canada and has become a citizen. Even the leader of the Canadian branch of the Tamil Tigers, Manickavasagam Suresh, arrested in 1995 as a threat to national security and ordered deported, is still in Canada 13 years later.

Some Canadian authorities admit the vulnerabilities created by their laws and lax policies on matters like extradition. A June 2007 backgrounder on counterterrorism by the Canadian Security Intelligence Service (a kind of combined FBI-CIA) concedes, under the heading "Canada as a base for terrorist activities":