The European bumblebee, Bombus terrestris, was introduced into Japan from Europe in 1991 for pollination of tomato plants. Many ecologists had warned of biological invasion by this species, and in 1996 a naturalized colony was found in Hokkaido, indicating that the species had become naturalized. The Ministry of the Environment effected a new law, the Invasive Alien Species Act, in 2005 to protect Japanese native fauna and flora from invasive alien species. Heated arguments arose between conservation ecologists and agriculturalists about whether the law should regulate B. terrestris. To reach a scientific decision, we began a study to reveal the ecological impacts of B. terrestris and to develop methods to control its naturalization. On the basis of our results, the Ministry of the Environment classified B. terrestris as invasive and requiring regulation by law, but its use would be permitted on the condition that it be used only for agriculture and that measures to prevent escape be taken. This legal control of B. terrestris in Japan is a revolutionary trial that aims to achieve a state of mutualism between biodiversity and agriculture.