Abstract This study analyzes the Türkiye–European Union Customs Union not merely as a trade arrangement abolishing reciprocal tariffs, but as a multi-layered legal-institutional architecture that directly shapes Türkiye's economic sovereignty, technological autonomy, and industrial-policy capacity. Its central question is not "did trade grow?" but rather "within what order, and under whose rules, did this growth occur?" Accordingly, the article develops an original analytical framework that integrates the concepts of asymmetric integration, economic sovereignty, technological autonomy, and core–periphery hierarchy around a core notion of legal-institutional dependency, thereby elevating the work from a single-case description to a theoretical contribution adaptable to other instances of asymmetric integration. Methodologically, the study adopts a qualitative research design, combining document analysis, historical-institutionalist interpretation, and comparative reading within an in-depth single-case study. The primary data are drawn from foundational legal documents—Association Council Decision No. 1/95, the Ankara Agreement, the Additional Protocol, and the official statement of the Ministry of Foreign Affairs—with each provision matched to its corresponding theoretical concept to form a systematic and traceable chain of evidence. The findings reveal a clear tension between the textual symmetry and the substantive asymmetry of the Decision. Alignment with the Common Customs Tariff narrows Türkiye's foreign-trade sovereignty; technical legislation and standardization keep Türkiye in the position of norm-taker rather than norm-maker; the competition and state-aid regime restricts the space for selective, high-technology industrial policy; and the deep harmonization sustained in the absence of full membership generates obligation without representation and a persistent legitimacy deficit. The evidentiary chain of thirty-three findings supports the study's main hypothesis at approximately ninety-eight percent. Without denying that this structure has afforded Türkiye market access, export volume, and institutional discipline, the study stresses that its structural constraints cannot be overlooked. The core problem is not the existence of integration but the structural persistence of unequal integration; because this dependency was historically constructed, it can also be historically redesigned. The concluding section therefore develops concrete reform proposals, including strengthening representation mechanisms, securing simultaneous participation in third-country trade, expanding policy space in strategic sectors, and establishing a balanced architecture of judicial interpretation.