Since the end of the Cold War, international law has increasingly been challenged by states and other actors. Specific norms have also been challenged in their application by new realities and obstacles. This article focuses on these challenges as they arise from the development of cyberspace and cyber operations, and offers an overview of the main questions arising with regard to the application of international law to cyber operations. By analysing the application of the existing norms of international law to cyber operations as well as identifying their limits, the article offers an accurate lens through which to study the contestation or process of reinterpretation of some norms of international law. The objective of the article is not to deliver a comprehensive analysis of how the norms of international law apply to cyber operations but to provide an overview of the key points and issues linked to the applicability and application of the norms as well as elements of contextualisation, notably after the failure of the 2016–17 United Nations Group of Governmental Experts on Developments in the Field of Information and Telecommunications in the Context of International Security. The article comprises three parts. The first part focuses on the applicability of international law to cyber operations. The second part identifies challenges that affect the applicability and application of international law in general, while the third part analyses challenges that affect specific norms of international law, highlighting their limits in dealing with cyber threats.