Millions of Americans could become Canadians under Canada's Act C-3 citizenship rule

Lawyer Amandeep Hayer in Vancouver, Canada, tells AP that the number of citizenship cases at his firm has gone from about 200 a year to 20 a day.

The reason is the Canadian Act C-3, which came into effect on December 15. It stipulates that anyone born before that date who can prove that they are related to a Canadian in a direct line of descent - through a grandparent, their parents or further back than that - can obtain citizenship.

That's the case for millions of Americans, many of whom are now applying for dual citizenship. More than 56,000 applications have been registered, according to Canadian authorities.