By Cheryl Dine
On Monday 31st March, 2025, City Law School welcomed Dr. Gesa Kübek to formally launch her book ‘EU Trade and Investment Treaty-Making Post-Lisbon: Moving Beyond Mixity’. This book launch was a public event that brought together EU, trade and investment law academics to explore the evolving landscape of EU trade and investment agreements in the post-Lisbon era.
Dr. Kübek’s book critically examines the evolution of EU treaty-making following the Lisbon Treaty, particularly the shift away from mixed agreements – where both the EU and its member states share competence. In her book, she argues that the EU is increasingly asserting exclusive competence over trade agreements, reshaping the legal and political dynamics of bilateral trade and investment treaty making. According to Dr. Kübek, “mixity in the field of trade and investment has become a matter of substance” as opposed to Heliskoski’s (2001) traditional view of mixity as a “procedural choice”.
During the book launch, Dr. Kübek explored how the practice of mixity has evolved over time. Fast forward to the 2020s, the notion of ‘mixity’ seems to involve deeper substantive considerations, including political, legal, and constitutional complexities. One of the key takeaways from Dr. Kübek’s analysis is that there is a growing tension between EU institutions and its member states in regards to the division of powers in external trade relations. For instance, Belgium’s decentralised constitutional structure, which adds another layer of complexity to the mixed procedure calling for a substantive design in EU’s recent treaty-making.
The Court of Justice of the European Union (CJEU) was also a core point of discussion in terms of its role in defining the limits of the EU’s exclusive competence, as seen in Opinion 2/15, which established a value-driven trade policy and allowed for a practical divide between trade and investment.
Dr. Kübek highlighted that mixity has largely been a political choice in the field of trade and investment (facultative mixity) and suggested that the choice between EU only and mixed agreements in areas of shared competence should be applied on a case-by-case basis rather than as a matter of principle. The EU-UK Trade and Cooperation Agreement (TCA) was a notable example of a facultative mixed agreement, strategically designed to avoid complications in ratification and Brexit negotiations, which, according to Dr. Kübek, could have been all the more complicated had the EU-UK TCA not been structured as a facultative mixed agreement. The approach demonstrated how mixity has become a more intentional and informed process in treaty-making, influencing both legal and political strategies.
Following Dr. Kübek’s detailed presentation of her book, Professor David Collins provided additional insights during the discussions, addressing key challenges and considerations surrounding mixity. He queried the role of mixity in the ability of EU member states to sign investment treaties with non-EU countries. One observation he raised was that the World Trade Organization’s General Agreement on Trade in Services (GATS) schedules are noticeably mixed. Dr. Kübek elaborated on the use of mixity in the field of investment and the competence of the Member States to sign and maintain their own investment agreements with third states before such agreements are ‘grandfathered’ by the EU (Regulation 1219/2012).
Prof. Collins raised several other critical questions concerning state-to-state investment settlement mechanisms and whether they could be inserted into investment treaties without requiring parliamentary involvement. He prompted Dr. Kübek to explore the implications of mixity in multilateral treaties in the context of institutions such as the IMF and the World Bank.
Referencing Chapter 3 of Dr. Kübek’s book, Prof. Collins questioned whether the EU’s divergence in rationale for investment protection – potentially leading to internal disputes and complex case law – was a factor in its gradual shift away from investor-state dispute settlement (ISDS). He also sought clarification on the EU-UK TCA, noting that some of the service commitments in the agreement remain fairly limited.
Finally, Prof. Collins reflected on the broader implications of mixity for EU governance. In that the primary focus may shift toward managing internal disintegration rather than pursuing deeper integration. He raised an important question in direct relevance to Dr. Kübek’s book: Could the EU truly move beyond mixity, or would political realities and legal constraints continue to make it an indispensable tool for treaty-making?
This is where Dr. Kübek’s three key propositions come into play. In her book, Dr. Kübek does not only explore markedly intellectually stimulating factors but also makes an intriguing conclusion on the EU’s “move beyond mixity” in the following propositions:
- Negotiators must carefully weigh the benefits of mixity (eg, making more comprehensive agreements) against the costs of including a multitude of veto players (eg, increased uncertainty about entry into force). For trade agreements, this balancing exercise principally tilts in favour of the effectiveness, unity and certainty that the EU-only procedure provides.
- The question of how national parliaments can be involved more closely in the process of making EU trade and investment agreements arises for EU-only and mixed agreements alike. Yet, the rationale for and the best way of doing so may differ depending on the character of the agreement.
- Facultative EU-only agreements or facultative mixed agreements should be made on a case-by-case basis, rather than purely as a matter of principle.
In sum, Dr. Kübek’s book presentation provided timely insights into the future of EU trade and investment agreements. As the EU navigates geopolitical shifts both internally and in response to its trading partners, on-going Brexit-related trade complexities, and the pursuit of sustainability-oriented trade policies, its approach to treaty-making will continue to evolve. The move beyond mixity has led to more informed and intentional treaty-making, prompting crucial questions about power dynamics. For instance, who has power, and who can and should wield it in shaping international agreements.
The book launch event at City Law School highlighted the importance of continued scholarly engagement in this area. As new trade negotiations unfold, Dr. Kübek’s work serves as a crucial resource for understanding the intricate legal frameworks governing EU external relations.
For those interested in EU trade law or international economic law, EU Trade and Investment Treaty-Making Post-Lisbon: Moving Beyond Mixity is a must-read, offering a comprehensive analysis of one of the most dynamic areas of EU law.
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