The New York Times has an op-piece, Sell the Tiger to Save It (via Biopolitical, from Cafe Hayek),
In pragmatic terms, this is an extremely valuable animal… A single farmed specimen might fetch as much as $40,000; the retail value of all the tiger products might be three to five times that amount.
Yet for the last 30 or so years, the tiger has been priced at zero, while millions of dollars have been spent to protect it and prohibit trade that might in fact help save the species. Despite the growing environmental bureaucracy and budgets, and despite the proliferation of conservationists and conferences, the tiger is as close to extinction as it has been since Project Tiger, a conservation project backed in part by the World Wildlife Fund, was launched in 1972 and adopted by the government of India a year later.
If we truly value the tiger, this crisis presents an opportunity to help it buy its way out of the extinction it now faces. The tiger breeds easily, even in captivity; zoos in India are constantly told by the Central Zoo Authority not to breed tigers because they are expensive to maintain. In China, which has about 4,000 tigers in captivity, breeding has been perfected. According to senior officials I met in China, given a free hand, the country could produce 100,000 tigers in the next 10 to 15 years…
At present there is no incentive for forest dwellers to protect tigers, and so poachers, traffickers and unscrupulous traders prevail. The temptation of high profits, in turn, attracts organized crime; this is what happens when government regulations subvert the law of supply and demand.
But tiger-breeding facilities will ensure a supply of wildlife at an affordable price, and so eliminate the incentive for poachers and, consequently, the danger for those tigers left in the wild.
Exactly the same argument can be made for the rhinoceros. I don’t know about the other four species of rhinoceros, but the White Rhino can easily be herded and bred in captivity.
Breed it, sell it, and save it.
Fishing Expedition 
Sue Lieberman of WWF-International says: “We’re afraid that poachers living near the world’s last populations of tigers may kill them to supply illegal markets that are likely to develop alongside any new legal ones.” (source: http://www.panda.org/about_wwf/where_we_work/asia_pacific/where/china/news/index.cfm?uNewsID=23498).
Has this ever happened before with other species? In practice, if there is a legal system of breeding tigers, the price for captive-bred animals (low effort) should normally be lower than for those which are wild caught (effort intensive). As a result, theoretically the incentive for people to go into the forest to kill a tiger would be much reduced.
I agree. Sue Lieberman misunderstands the nature of markets. You can’t just outlaw them and expect them to disappear, look at the War on Drugs.
See also this, http://www.mng5.com/papers/DeathKiss.pdf