The killing of Cecil the lion in Zimbabwe earlier this year by Walter Palmer, a US dentist, caused a global outcry against the hunting for sport of the animal.

In response, US authorities have now decided to classify lions as an endangered species. The designation by the Fish and Wildlife Service will now make it extremely difficult not only for hunters to import trophies into the country but will also institute strict regulations on bringing live lions into the US. The new rules are scheduled to go into effect by January 2016.

The African lion has increasingly been in danger of extinction. Over the past two decades, the population of the Panthera leo, as they are known, has declined by 43%, according to the International Union for Conservation of Nature (IUCN). In West Africa, only 400 are left. Overall, estimates suggest that there are about 20,000 lions left in the continent. The IUCN classifies the species as being “vulnerable” to extinction.

In November, the French government stopped issuing permits for the imports of lion trophies. Meanwhile, the British have said that if authorities in Africa don’t step up efforts to improve the conservation of the endangered animals and hunting organizations don’t reform, they too will ban trophy imports by 2017.

While US authorities don’t have the jurisdiction to impose their restrictions abroad, they are hoping that the new rules will encourage countries that host hunters to regulate the sport for conservation purposes.

Nevertheless, conservation groups in the US have welcomed the decision to regulate hunting imports, saying that it is an important step forward. ”This is huge, and we’re really excited,” Jeffrey Flocken, the North American regional director for the International Fund for Animal Welfare, told the New York Times.