In an era characterised by resurgent geopolitical tensions, the role of nuclear deterrence is once again at the forefront of European defence strategy. Traditionally seen as a military safeguard, nuclear deterrence evolves into a complex legal construct, raising concerns about its legitimacy, constraints, and adaptability. As the Russian invasion has reignited debates over nuclear strategy, it becomes clear that the legal dimensions of deterrence reflect both a continuity of Cold War-era principles and a significant shift toward flexible, adaptive policies. 
Given the potentially disastrous effects on civilian populations, the current legal framework raises severe humanitarian questions, even though nuclear deterrence serves as a critical safeguard. Therefore, by exploring the legal basis of nuclear deterrence and its role within Europe’s defence architecture, this article highlights the need for scrutinised legal adaptability in a rapidly evolving security landscape. Maintaining credible deterrence while ensuring compliance with legal obligations and humanitarian principles remains essential to reduce civilian casualties.