Johannesburg (CNN)South Africa's first online auction of rhinoceros horn is underway, with more than 500 kilograms up for bid from Wednesday through Friday.
On Sunday, the High Court in Pretoria paved the way for the controversial auction, ordering the minister of environmental affairs to hand over a permit for the sale of 264 rhino horns to breeder John Hume.
Hume, who owns the world's largest private collection of rhinos, has battled to overturn a ban on the sale of horn in South Africa for years.
The Private Rhino Owners Association estimates in the eight years the ban has been in place, owners have spent more than $100 million to protect their rhinos. Without the sale of horn, the association argues, the breeding of rhinos would become unsustainable.
But environmental groups say there is no conservation value in the auction, arguing that rhinos shouldn't be seen as livestock.
"The focus of conservation should be on wild rhinos," says Christina Pretorius of the International Fund for Animal Welfare (IFAW). "Rhinos can't produce enough horn on a regular basis to stem the insatiable demand."
According to the World Wildlife Fund the number of rhinos poached in South Africa has increased by 9,000% since 2007. Their horns can fetch up to $100,000 per kilo in illegal black markets in Asia, where it is mistakenly believed to have medicinal benefits. The horns are made of keratin, the same protein in human fingernails.
Last year, more than 1,000 South African rhinos were slaughtered for the fourth year in a row. There are now fewer than 20,000 rhinos left in the country, home to 80% of the world's rhino population.
The ministry says it will heavily monitor the sale and all horns will be required to stay in South Africa in keeping with the 40-year international ban on the trade.
But the IFAW's Pretorius says it will be nearly impossible to monitor the sale. "Frankly we don't believe any system exists to put in place the checks and balances to prevent these horns from getting into the black market."
The owners' association says all potential buyers must first apply for permits and give a 100,000 rand deposit. There are no listed prices on the site, with the horns going to the highest bidder.
CORRECTION: This story has been updated to correct the name of the World Wildlife Fund.