This paper reconsiders the trade remedies and subsidy control regimes of the European Union (EU) through the lens of “ocean stewardship”. It claims the EU's economic instruments exhibit a profound normative shift from the role of shield for defensive market regulation to sustainability governance in a proactive form. Historically the function of trade remedies and state aid disciplines has been to provide a shield for market stability, with competitive neutrality and counteracting unfair behaviour at the cornerstone of their objectives. However, under the developing framework of the European Green Deal, the Blue Economy Strategy, and the Trade and Sustainable Development (TSD) agenda, the emphasis of these instruments, or their application, has increasingly pivoted toward ecological responsibility and conservation of the oceans. This study contextualizes the EU trade and subsidy control regimes within a broader regime of normative power, where fairness in economics, environmental integrity, and governance of the ocean is constitutive rather than separate policy arenas. This normative reassessment of the regimes presents a unique instance of “sustainable market governance” and positions the EU as the global standard setter to promote climate justice and protect the oceans through trade regulation. However, this paper also questions the possible tensions of this approach and highlights the risks of green protectionism, extraterritoriality, and fragmentation between trade and environmental regimes. It notes that the EU's legitimacy as a leader depends on developing a coherent, transparent, and collaborative governance approach that balances competitiveness and stewardship while embedding sustainability into the principles of international economic order. Ultimately, the paper develops a critical vision of how trade defence and subsidy control, once vehicles of market insulation, can become regulatory conduits for ocean sustainability and global environmental governance.