The arrests of suspected terrorists at the Canadian border this month have bolstered supporters of a controversial law that would require the tracking of every foreigner entering the United States.

That law is set to take effect in 2001, but lawmakers from northern states have been trying to junk it for years, arguing that it will create long lines at the border and deter tourists.

But with recent arrests in Washington state and Vermont that have fueled heightened fears of terrorism, the law's backers have new ammunition.

Ahmed Ressam, an Algerian, was arrested in Washington state and charged with attempting to bring bombmaking materials into the country. He has pleaded not guilty. Investigative sources said there are indications he may have received terrorist training in Afghanistan or Algeria.

Lucia Garofalo, a Canadian woman, and Bouabide Chamchi, of Algeria, were charged in Vermont with conspiring to misuse a false passport and offenses related to the transportation of aliens into and inside the United States. Prosecutors said she has ties to a terrorist group.

"This case is the best wake-up call that either Canada or the U.S. are going to get about our porous shared border," said Rep. Lamar Smith (R-Tex.), who chairs the House Judiciary's subcommittee on immigration and is the chief defender of the law.

States bordering Canada have warned that should the law go into effect as scheduled, it would cripple trade and tourism. Besides, they say: Border guards did not need the law to apprehend Ressam.

"There might be some heightened concerns about the recent reports, but [the arrest] shows that the current efforts are working," said Sen. Rod Grams (R-Minn.), who is co-sponsoring a bill to repeal the measure.

The law, Section 110 of the Illegal Immigration Reform and Immigrant Responsibility Act of 1996, requires the Immigration and Naturalization Service to devise an automated system to track the entry and exit of all noncitizens.

The Senate has voted three times to repeal the law, including this year, but the House has yet to go along. Last year, congressional and White House negotiators agreed to delay the law's start-up until 2001, giving the INS time to develop a workable plan.

But opponents of Section 110, led by Sen. Spencer Abraham (R-Mich.), say the law would lead to long lines at the border and cripple tourism and trade. And, they point out, it might not be needed.

"The one thing we can say is that we caught this guy," said Ali Cleveland, manager of labor policy for the U.S. Chamber of Commerce, referring to Ressam. "The Border Patrol did their job, was suspicious, he ran, but eventually was apprehended."

But proponents of the law say the three arrests show the need for increased security. Dan Stein, director of the Federation for American Immigration Reform, blames Abraham for the controversy.

Stein predicted that the arrests will strengthen the hand of his organization and its allies.

"The porous nature of our northern border is inappropriate to the modern age," he said. "The legacy of the world's largest unguarded land border will soon be history. What we need is a land border that requires inspections."

Abraham's spokesman, Joe Davis, declined to respond to Stein's accusations but said the law would not have helped Border Patrol officers identify those arrested.

"Implementation of 110 is unrelated to the recent incidents," he said. "The purpose of the law is to track people who have stayed in the country too long, not people who have false documents."

Canada strongly opposes the law, but Section 110 advocates say that a recent study by the country's own intelligence agency, the Canadian Security Intelligence Service, buttresses the case for retaining it.

"Proximity to the United States, a common border, large expatriate communities and a healthy economy draw representatives of virtually every terrorist group in the world to this country," the report states. "Support networks in Canada have provided terrorists with safe-haven and transit to and from other countries, including the United States."