A campaign group has taken court action in South Africa over the removal of an advertisement urging President Jacob Zuma to ban the trade in lion bones.
The advert, showing a lioness looking down the barrel of a gun with Mr Zuma in the background, was removed from the main airport in Johannesburg last year.
Campaign group Avaaz said airport authorities violated freedom of expression by pulling down its advert.
Asia is a lucrative market for lion bones, used in traditional medicines.
Official statistics show that South Africa increased its export of lion bones by 250% between 2008 and 2010, Avaaz says.
It placed the advert at OR Tambo International airport to target tourists, it says.
Famous game parks
The Airports Company SA (Acsa) ordered its removal after nine days because of the potential "public relations disaster" for South Africa, the Johannesburg High Court heard, according to the South African Press Association (Sapa).
The advert said, "Our lions are being slaughtered to make bogus sex potions for Asia. Will President Zuma save them? Urge him to stop the deadly bone trade now."
Acsa communications chief Solomon Makgale had objected to the advert because of its "implicit message" that Mr Zuma was "standing by while our lions are being killed and is thus complicit in the killings", Avaaz lawyer Stephen Budlender told the court, Sapa reports.
However, the advert was not defamatory nor did it promote hate speech, he is quoted as saying.
Its removal was in breach of Avaaz's constitutionally enshrined right to freedom of expression, Mr Budlender added.
South Africa's Environment Minister Edna Molewa told parliament in May last year that a moratorium on the trade in lion bones could not be imposed because it did not "negatively impact on the survival of the species in the wild", local media reported at the time.
The lion bones being exported came from "canned hunting" farms, where lions are bred for commercial purposes, rather than from the wild, she was quoted as saying.
Many foreigners visit South Africa to see wild animals at famous game reserves such as Kruger National Park (KNP) and Hluhluwe Umfolozi.
In March, conservationists said the population of Africa's lions had fallen by about 80% over the last 50 years and there could be as few as 20,000 to 30,000 of the big cats left in the wild.
However, fencing at parks in South Africa and Tanzania had helped the populations to grow, they said.
Some of the big cats have been killed because they are perceived to be a threat to livestock, and competition for land and over-hunting of their prey have reduced their numbers even further.