Both America and Europe banned bringing seal products into their countries, and the trade in Canada dropped off.
But now demand for fur - including seal skins - is back, with countries like Russia and Poland wanting them to make hats and clothes.
The International Fund for Animal Welfare (Ifaw) wants Canada to put an end to the killing.
"The Canadian Government has given the go ahead for up to one million seals to be killed over the next three years.
"This is a cruel and barbaric hunt and we want to see an end to it today," Stella Green, marine campaigner for Ifaw told CBBC Newsround Online.