The development of frontier AI models is concentrated in a few companies and countries. The governments of these countries have shown both the legal power and the political will to decide which other countries may use these systems. In June 2026, the United States required a leading developer to obtain licenses before releasing its most advanced models to any foreign person, including foreign nationals resident in the United States. The affected models were withdrawn worldwide at short notice, partly because the restriction proved impractical to administer. This followed within months of the first documented case of a largely autonomous, AI-run cyber espionage campaign, and coincided with mounting evidence that frontier models alter the economics of both cyber attack and cyber defense. This article examines how these two developments interact, and situates them within the unusual market dynamics now driving large-scale AI development. It argues that access to frontier AI is becoming part of national cyber defense, that such access can be revoked, and that the obvious remedy of sovereign capability remains only partly feasible for all but a handful of states. Drawing on evidence about training costs, the concentration of computing power and the support offered by national AI programs, it asks what sovereignty can realistically mean for small and middle powers, and for large powers as well. The article proposes a layered strategy: negotiated access guarantees, sovereignty at the level of inference, hedging with open-weight models, pooled regional capability, sustained talent development and continued investment in basic cyber resilience. The open-weight hedge proves at once more capable and more politically exposed than is commonly assumed. Much of the near-term risk lies in how capable models are deployed and contained rather than in their apparent performance. Blogger's Review: The development and deployment of frontier AI will have significant implications for national cyber security and sovereignty. In the face of these challenges, countries need to take proactive strategies, including negotiating access guarantees, developing indigenous capabilities, and engaging in international cooperation, to ensure their own cyber security and AI development sovereignty.