Influence through institutional ecosystem. The European Parliament and the parliamentarization of international agreement negotiations

The European Parliament (EP) is often actively involved in the negotiation of international agreements, beyond its veto power on their ratification. Moreover, the EP has influenced the substantive content of several international agreements. This influence is often considered as a result of EP veto-leveraging vis-à-vis the Commission, which is the institution negotiating on behalf of the EU. But this perspective is insufficient, as in practice the EP tends to support agreements in principle and to engage in a cooperative way. To connect these approaches into a more encompassing account of EP influence, we conduct a theory-building process-tracing analysis of the EU-Vietnam Free Trade Agreement (2020) and the Advanced Framework Agreement with Chile (2024). We develop a causal mechanism functioning under four scope conditions: EP veto power over ratification, pre-existing practices of inter-institutional interaction between the EP and the Commission, EP support for ratification in principle, and agreements relatively important to EP actors. Under these conditions, informing the EP of a negotiation activates an institutional ecosystem comprising various activities through which EP actors are involved. These activities allow them to exchange information and express preferences to both Commission and third country actors. Because this ecosystem is underpinned by a problem-solving dynamic and because EP involvement is focused on its ‘pet issues’, its preferences are integrated in the agreement itself and in ‘add-ons’. In this context, the perspective of an EP veto is not directly or permanently present for involved actors