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The sudden exodus to Canada was caused by the Safe Third Country Agreement signed by Ottawa and Washington in December 2002. The treaty takes effect Wednesday and is meant to prevent what officials in both countries call "shopping for asylum." It requires refugees seeking asylum to do so in whichever country they reach first.
Canada is generally considered the more liberal of the two countries in refugee matters, but it is more difficult to reach than the United States because it receives international flights from far fewer countries and there are more American consular offices around the world to process claims.
Officials said the agreement would enhance the orderly handling of asylum claims in two countries historically committed to the protection of refugees.
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Advocates {for refugees} on both sides of the border expressed disappointment that Canada pushed for the agreement. "I feel that this brings back echoes of the worst in Canada's history," said Janet Dench, executive director of the Canadian Council for Refugees, referring to when Canada refused to open its doors to European Jews fleeing Nazi oppression.
Beginning on Wednesday, immigrants who travel through the United States and seek asylum in Canada, at a point of entry on the border, will generally be sent back to the United States to apply for asylum.
http://www.nytimes.com/2004/12/28/international/americas/28canada.html