Despite initial intentions to better align transatlantic regulation and associated practices in the negotiation of the Transatlantic Trade and Investment Partnership (TTIP), this was not possible for rules concerning genetically modified organisms and data privacy. By 2016 both matters effectively fell off the TTIP negotiating agenda. This paper identifies the factors responsible, specifically the critical role played by independent regulatory agencies and associated bureaucratic politics, transnational coalitions of private sector organizations, and non-government organizations and contingency. These factors are not exclusive to the two salient regulations considered here, with the implication that the identification of cross-border spillovers is at best a necessary condition for the successful negotiation of binding trade rules on behind-the-border government policies.