In this essay I have examined the legal protection against the threat to the biological diversity that the import of pet animals and the releasing of them into the environment can result in. I’ve focused on non-indigenous rodents as they are being imported to Sweden to be kept as pet animals. There are regulations for import of pet animals within the EU and from countries outside of the EU, but these mostly regulate the import of common pets, for example dogs and cats. The main objective of the regulations is to provide animal welfare, not protection of the biological diversity. Notwithstanding the fact that non-indigenous rodents could mean a serious threat to the biological diversity if being introduced in the natural environment, the regulations in principle permits free import of up to five rodents. Furthermore there are no prohibitions concerning the release of pet animals into the environment which conduces to a weak legal protection for the biological diversity.