During the SARS outbreak in 2003, when a number of countries placed travel restrictions on Canadians and the World Health Organization issued an advisory urging travellers to avoid Toronto, an epicentre of the outbreak, the federal government objected vociferously, saying there was no justification for those moves.

Canada subsequently pushed hard for the International Health Regulations, a treaty that, among other things, says any such restrictions on travel must be be backed by good science.

Yet, in response to the remote threat of Ebola coming to Canada, the federal government has imposed a 90-day wait on the issuing of visas for anyone who has travelled or even plans to travel to the hardest-hit countries – Guinea, Liberia and Sierra Leone. Public-health experts say the move, among the toughest responses worldwide, contradicts current science.

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In discussions over the past few days – including a Saturday conversation between Immigration Minister Chris Alexander and WHO director-general Margaret Chan – Ottawa has defended its decision. It argues it has not imposed a general ban on travel – forbidden under the international regulations – since it allows for existing visas to be honoured, and it excludes Canadians themselves.

Australia has taken a similar tack: It has cancelled all visas for travellers from the Ebola-stricken countries and it said permanent visa holders will have to submit to a 21-day quarantine.

Amir Attaran, the Canada research chair in law, population health and global development policy at the University of Ottawa, said in 2005, "Canada was ardently advocating that countries had to be extremely cautious and methodical on rules based in their application of visa bans and other restrictions."

With the new rules, he argues, Canada is restricting visas on people passing through Canada with an "intent to eventually travel to West Africa, as well as extend the general restriction more than four times longer than the incubation period for the virus."

It is accepted science that a person cannot fall ill or transmit the virus more than 21 days after exposure.

Mr. Attaran also said the claim that Canada is not breaching those rules, based on technicalities, is hypocritical, with potentially long-term ramifications. "If we are ever back to another SARS situation, where we are the country facing the travel restrictions, do you think the WHO will give us a millimetre of slack? What comes around, goes around."

David Fidler, director of the Indiana University Center on American and Global Security who has served as a legal consultant to the WHO, was also harsh in his criticism. "The Canadian government is playing games because it cannot satisfy its obligations under international law with regard to science and public health."

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He said the decision is particularly jarring considering Canada's long-standing reputation in the area. "This is not what global health leadership looks like."

An Immigration Canada spokesperson insisted that, in this country, decisions would still be made on "a case-by-case" basis, citing the ministerial discretion that is always an option in immigration cases, and that this would allow wiggle room for "essential travel."

"We have instituted a pause," department spokesperson Jean-Bruno Villeneuve said on Sunday, "but there is room for discretion if we can be assured someone is not infected with Ebola."

Canada's approach was initially criticized by the WHO for using a loophole to get around the 2005 IHR treaty, which clarifies the authority of the organization to set international travel guidelines during epidemics, and requires countries adopting more severe restrictions to provide scientific and public health evidence to support them. As it stands, the WHO has only recommended restricting the travel of infected patients, or people who have be identified as coming into contact with Ebola patients – not including "well-protected health care workers."

Despite repeated requests to immigration officials Sunday, no information was provided to support the policy change, which was announced late afternoon on Friday.