Their cases are being considered by the Canadian legal authorities, who are assessing whether they face "genuine fear of persecution" if they are sent back.

Hundreds of Americans have crossed the border into Canada in recent months following clampdowns ordered by the attorney general, John Ashcroft, on medicinal marijuana clubs that exist in states where voters have passed measures approving them.

They provide marijuana to patients suffering from cancer, Aids, multiple sclerosis and glaucoma and whose doctors have suggested the use of the drug.

This week, the California supreme court ruled that Californians who grow or use marijuana for personal medicinal needs are protected from prosecution in state courts if they have approval. But the federal government is fiercely opposed to this and is continuing its prosecutions in federal courts.

The Drug Enforcement Administration (DEA) recently raided medicinal marijuana clubs in LA and San Francisco, a process upheld by the US Supreme court.

Some who have crossed the border are wanted on marijuana charges in the United States and the US authorities are pressuring Canadian law enforcement agencies to send them back. The moves come as Canada, like the UK, is liberalising its laws on cannabis.

One of the best known American fugitives in Canada is Renee Boje, whom the US wishes to extradite to stand trial for cultivating cannabis plants at the home of Todd McCormick, a cancer patient and medicinal marijuana activist in LA. She had watered the plants on his behalf.

"I'm a member of a class of society they're trying to oppress or wipe out completely," Renee Boje told the online news network, AlterNet from her home in Vancouver, British Columbia.

If convicted, she faces a minimum sentence of ten years. The length of that sentence is part of her plea that she faces unjust persecution if she were to return home. "There are hundreds of Americans here because they are being persecuted by their own government."

Another American, Steve Kubby, the Libertarian Party's 1998 candidate for governor of California, and Ken Hayes, who operated the 6th Street Harm Reduction Centre in San Francisco, have also entered Canada.

Kubby, who has adrenal cancer, faces a 120-day jail term for drug possession. Additional charges, filed since he arrived in Canada, of conspiring to grow more than 1,000 plants, mean that he could face a sentence of ten years or more.

Both men have now formally claimed refugee status under the UN refugee convention on the grounds that they have a "well-founded fear of persecution" in the US. Canadian immigration officials have allowed them to stay while their status is determined in court.

"US officials have violated the law and intentionally targeted the leaders of the medical marijuana movement by using conspiracy charges," said Kubby. "I'm being threatened with a death sentence. How can anyone justify that and say it's not an attempt to persecute me?"

Their claims have been attacked by the White House drugs policy adviser Robert Maginnis who said on Canadian TV: "Providing sanctuary to some of these people who see Canada as an easy place to escape the long leash of US law enforcement is dangerous ... I would hope that the Canadian government would see fit to send them back to the US so they can face charges."

The Canadian federal government has granted permits to possess or grow marijuana to more than 800 Canadians who suffer from Aids, cancer or multiple sclerosis.

Many of the American refugees are now growing their own marijuana through such medicinal marijuana clubs as the Vancouver-based Compassion Club, which estimates that over 100 of its 2,000 clients are Americans.

Canada became a refuge in the sixties and seventies for people who did not want to fight in the Vietnam war, a journey memorialised in the song, My Uncle, by the Flying Burrito Brothers, who sang of "heading for the nearest foreign border/ Vancouver may be just my kind of town/ 'Cos they don't need the kind of law and order/ That tends to keep a good man underground."

The "war on drugs" is now propelling others towards that same foreign border.