見つけました。やっぱりCanadian Motor Vehicle Safety Standards (CMVSS) の規格にあってないとダメみたいですよ。リンクを貼っておくので、そこのShopping for a Child Restraint Systemを読んでみてください。http://www.safekid.org/carTC.htm
The regulations in BC require any child seat have a label on it stating that it complies to Canadian Motor Vehicle Safety Standards (CMVSS) 213 213.1 213.2. The seats which are sold in the US do not have these compliance labels, therefore it would be illegal to use them in Canada. The best way to be sure that a child seat complies with Canadian standards is to buy it in Canada.