Cyberspace: A new branch of international customary law?

International relations between countries increasingly take place in cyberspace. From concerns about cyber security and Internet surveillance to privacy to harmful speech - state and non-state actors developed practices and normative conceptions that could be regarded as international customary law in statu nascendi. The aim of this contribution is to present arguments supporting the thesis that research concerning international law should be broadened to include cyberspace. Due to lack of treaty law in this area, one shall resort to a second source of international law, namely custom especially, as one eminent researcher has noted: 'there are still numerous branches of international law regulated by customary law, and still more important, new rules of that law are raising'. The article presents the theory of custom as a source of international law and methods of evidencing it in the context of cyberspace and then outlines areas where such norms could have developed and therefore could be used to settle disputes between states.