John Hume owns 5 percent of the world's rhinos. Last year, he sued the South African government to legalize the sale of rhino horn. The case reached South Africa's equivalent of the Supreme Court this summer. In a nation that's home to 70 percent of Earth's rhinos, this is a question of what conservation is in the 21st century. Could selling horn, the very part that rhinos are killed for, actually save the population?