This paper examines the role of law as a structuring instrument in the transition towards a circular economy, framed within the strategic goals of the European Green Deal and the 2030 Agenda. Moving beyond a merely environmental or technical interpretation, the study conceptualises the circular economy as a legal paradigm with transformative potential across economic, institutional and social dimensions. The research is guided by the central question of whether the current European and Spanish legal frameworks are adequately configured to ensure a coherent, effective and equitable transition to circularity. The analysis combines a legal-dogmatic and qualitative methodological approach, focusing on the main European directives and regulations, as well as their transposition into Spanish law. It critically assesses the effectiveness, coherence and enforceability of the current legal architecture, identifying major regulatory challenges such as fragmentation, asymmetric implementation, digital gaps and weak justiciability. The study proposes five strategic legal priorities to enhance the system: regulatory harmonisation, strengthening of extended producer responsibility (EPR) mechanisms, promotion of green taxation and circular procurement, reinforcement of local capacities, and the mandatory integration of digital traceability tools. As a case study, the maritime sector is examined as a dense legal environment where environmental, technological, labour and gender dimensions converge. Particular emphasis is placed on the need to integrate gender equality into circular economy policies, especially in masculinised and strategically relevant sectors such as shipping and port infrastructure. The findings support the thesis that law must no longer be treated as a subsidiary technical instrument, but as a key enabler of systemic change capable of articulating sustainability, innovation and social justice. The paper calls for a new legal pact underpinning the circular economy, based on enforceable rules, multilevel governance and inclusive design, ensuring that circularity is not only operational but also socially transformative.