It is ilegal to release a tiger, too - but they are also furry enjoyable animals, so let's have a few in every wood!
You jest elegran, but the Lynx Trust has been fighting to reintroduce the lynx into Kielder Forest and other sites in the UK, on the grounds that it used to live here hundreds of years ago before being driven out by human development.
They claim that the lynx would present no danger to humans and that they will curb the deer population.
So killing members of one species by exposing them to a new predator is ok, but culling them is not 
I can understand wanting to conserve a species in an environment where they are already living, but reintroducing a long-gone species without knowledge of the consequences seems rather risky and a bit of a vanity project.
It seems that Northumberland County Council take a dim view too as the Trust has been refused permission.