How do the parliamentarians (de)legitimize EU the treaty reform?

More than a decade after the last modification of EU primary law, discussions on altering EU treaties are underway within the realm of EU institutions and expert circles. The European Parliament stands as a front runner in this endeavour, having exercised its authority by calling heads of state and government to establish a Convention for revising EU Treaties in May 2022, in response to the Conference on the Future of Europe (CoFoE). In a counter move, a group of 13 Member States published a non-paper opposing the "hasty" initiation of treaty revision procedures, thus representing rather sceptical position of a formidable block of national interests whose agreement is pivotal for the reform process. Yet, the underlying factors influencing support or resistance to treaty changes remain relatively unexplored. This research seeks to examine the strategies of (de)legitimization within the EU treaty reform discourse in the "multilevel parliamentary field". To this end, we conduct content analysis of plenary debates within the European Parliament, along with six national debates in the Czech, Slovak, Polish, Italian, German, and French parliaments. Additionally, we analyse three debates held during inter-parliamentary committee meetings (ICMs) within the Committee on Constitutional Affairs (AFCO). All these debates span from 2020 to 2023 and revolve around topics related to the CoFoE. This three-level analysis allows us to map various (de)legitimization strategies, taking into account factors such as partisan affiliations, nationality and the influence of the specific multilevel parliamentary platforms (transnational, national or inter-parliamentary).