Drawing on the multi-level perspective of socio-technical change and social practice theory, this paper argues that macrosocial marketing must attend to the challenge of aggregate demand reduction in order to support transition to more sustainable marketing systems. However, reversal of current production and consumption system trajectories is a prodigious challenge. To provide deeper insight into that challenge, an ethnographic case study of a failed plastic bag tax identified the mechanisms reinforcing unsustainable marketing systems. Despite widespread awareness and espoused support, the tax failed to meet policy goals. Embeddedness of plastic bags in two inseparable practices (waste management and household provisioning) gave rise to seven themes: Valuableness, skepticism, subversion, blame, juxtaposition, ubiquity and embeddedness, rights and responsibilities, highlighting the roles of habitus and dominant technological regimes, and the notion of markets as sites of conflict. Mapping the system mechanisms highlighted regulating loops locking in systems behaviors at macro (landscape), meso (regimes of technology and practice) and micro (individual consumer and firm) levels. Building on the idea of demarketing, a process of macrodemarketing is proposed as a multi-level challenge to systems unsustainability. A series of macrosocial marketing interventions is proposed, ranging from electoral and education policy, to incentives for closed loop supply chain innovations. Addressing the limitations of the voluntary individual choice perspective, the study contributes insight into sources of resistance and potential capitulation to systems interventions at multiple levels and among multiple stakeholders.