Objectives:
The article proposes a comparative public law theory of defence procurement based on the concept of capability sovereignty. The main objective is to show that defence contracts are no longer merely instruments of acquisition, but legal architectures through which the state governs dependence, technological maturity, operational availability, and future options. It aims to demonstrate how formal state ownership can easily mask material operational captivity in an era where sovereignty is lost through proprietary lock-in, software dependence, or inaccessible source code.

Methods:
This study employs a comparative public law methodology and doctrinal legal analysis to evaluate defence procurement frameworks, including Article 346 TFEU, Directive 2009/81/EC, and the 2025 SAFE/EDIP initiatives.

Results:
Analysis of Article 346 TFEU, Directive 2009/81/EC, and the 2025 SAFE/EDIP frameworks reveals that public law has transitioned from enforcing security exceptions to proactively enabling industrial readiness. Comparing French, EU, US, and NATO frameworks demonstrates that modern defence sovereignty is increasingly compromised by contractual, proprietary lock-ins and supply chain obfuscation rather than treaties or war. To mitigate these long-term risks across software, data, and modification rights, this article introduces a Sovereign Contract Audit Matrix.

Conclusions:
The findings argue that the relevant question is no longer whether sovereignty is national, European, transatlantic, or contractual, but at which level legal arrangements maximize the state’s effective freedom of action. By defining capability sovereignty as the legally, industrially, and technologically organized capacity to act without excessive dependence or delay, the article concludes that managing these contractual frameworks is essential to maintaining true strategic control during a crisis.