This episode dives into the doctrine of secondary trademark liability in both the United States and European Union, based on insights from The Cambridge Handbook of International and Comparative Trademark Law. Secondary liability holds third parties accountable for facilitating or contributing to trademark infringement, even if they are not the primary infringers. We unpack two key forms of secondary liability—contributory and vicarious liability—examining how they apply to platforms, distributors, and service providers. Through landmark cases like Tiffany (NJ) Inc. v. eBay Inc. in the US and the L’Oréal v. eBay decision in the EU, we explore how courts assess knowledge, control, and the role of intermediaries. This episode highlights the differing thresholds and legal tests for establishing secondary liability across jurisdictions, emphasizing the impact on online marketplaces and the obligations for trademark protection in a digital age.