Remanufacturing is a process of restoring used products to the same condition as new products. It has become a important practice in advancing circular economy by retrieving the remaining useful value and reducing material and energy consumption. The strategic significance of remanufacturing is increasing as firms and regulators strive to balance environmental performance with economic competitiveness. This study develops an exhaustive game-theoretic framework to analyze the strategic interactions among OEM, an independent remanufacturer, and a regulator within the context of Extended Producer Responsibility (EPR). Based on the literature on durable goods and remanufacturing markets, we model a three-stage game in which the Regulator, acting as Stackelberg leader, sets policy instruments, including collection targets, recycling standards, and potential credit mechanisms. The OEM and the remanufacturer then engage in simultaneous competition. Consumer heterogeneity and durability considerations yield a system of linear inverse demands that affect both the primary and secondary market prices. The equilibrium characterization signifies the threshold conditions on remanufacturing costs that governs full, partial or no remanufacturing choices. By considering both remanufacturing strategy and regulatory design, this study contributes to the theoretical understanding of the producer-remanufacturer competition under environmental policy and offers guidelines for implementing EPR schemes that align remanufacturing incentives with environmental objectives.