"Wolf reintroduction in Yellowstone has been the most popular and most environmentally justified endangered species reintroduction effort, " said O'Neill who also served as a lead attorney in the Exxon Valdez lawsuit.

CNN: Yellowstone wolves get their day in court

Recently, the reintroduction of once-native species to Scotland (such as elk, boar and wolves) caused fierce controversy at the Highland estate of Alladale, an idea that could seem laughable to the locals around Cairngorms National Park.

BBC: A Scottish-style safari

In 1997 the Farm Bureau and other groups sued to have wolf reintroduction declared illegal under the Endangered Species Act.

CNN: Wolves roaming western forests not yet out of the woods

Environmentalists were supposed to have their day in court in May to appeal the 1997 ruling by Wyoming District Court Judge William Downes that said the reintroduction of wolves into Yellowstone National Park was a violation of the Endangered Species Act.

CNN: Appeal of wolf removal rescheduled

The reintroduction of gray wolves into Yellowstone has become a rare success story in the battle to save endangered species in the United States.

CNN: Planet in Peril: Environmental Coverage - Special Reports from