Not only Japan but also Germany and Italy, they are also countries famous for their advanced technology and strong economy but they do not have the right to possess nuclear weapons. The reason is because they were the cause of World War II, and after being defeated, superpowers like the United States and Russia forced them to sign the Nuclear Non-Proliferation Treaty (NPT). To ensure that they will not shake the world again and in return they will have peace and receive protection from the US and the EU.