Treaties — Power to conclude — European Atomic Energy Community — Treaty-making powers of the Community and its Member States — Community possessing power to adopt internal legislation on subject — Whether possessing parallel power to conclude international agreements — Transport of nuclear material — Draft Convention prepared by International Atomic Energy Agency — Member States proposing to become parties without participation by Community — Whether Member States retaining power to act — Whether Community must also become a party — Convention imposing obligations which would require exercise of powers by Community — The law of the European Atomic Energy Community