Supply Chain Infiltration in Nigeria’s Alcoholic Beverage Sector: Mapping Illicit Network Structures and Downstream Vulnerabilities

Background: Counterfeit alcoholic beverages pose a major public health threat in Nigeria, yet their infiltration of legitimate supply chains remains poorly understood, especially in Sub-Saharan African markets where informality and weak regulation create conditions overlooked by mainstream counterfeiting models. Methods: This study utilised a qualitative multiple case design, drawing on eight enforcement cases and fourteen semi-structured interviews with retailers, distributors, regulatory officers and police. Results: The findings revealed a contradiction to global models built on the model of upstream adulteration or transnational smuggling. The findings revealed that counterfeiting in Nigeria operates domestically, whereby the supply chain is vertically compressed network in which manufacturing, warehousing, distribution and retail are operated as whole within residential and commercial premises. Three operational clusters are identified: vertically integrated illicit hubs (Cluster A), covert urban micro-production sites (Cluster B), and peripheral component and distribution nodes (Cluster C). Conclusions: Theoretically, the study extends Transaction Cost Economics by showing illicit actors invert conventional governance logic to minimise detection rather than transaction costs; enriches Principal–Agent Theory by demonstrating dual-agency equilibria in which downstream intermediaries serve legitimate and illicit principals simultaneously; and integrates institutional voids theory to explain why this infiltration regime self-reinforces under fragmented licensing and sporadic enforcement.