http://www.slate.com/articles/news_and_politics/jurisprudence/2015/07/how_to_prosecute_cecil_the_lion_s_killer_apply_the_endangered_species_act.html

Outrage continues to spread over Minnesota dentist Walter Palmer’s alleged killing of a lion in Zimbabwe, with new evidence emerging that Palmer may have also hunted several endangered species—including a leopard and white rhinoceros. Wounding or killing endangered species is illegal in the United States under the Endangered Species Act. But right now, Americans are free under U.S. law to travel overseas and slaughter as many endangered species as they want.