Summary In May 2023, Jichikenkyu published a paper titled "The European Union's Competence and Procedures for Ratifying the Istanbul Convention on Preventing Violence and Domestic Violence against Women" by Professor Yumiko Nakanishi at the Graduate School of Law. The paper discusses a court opinion regarding the European Union's (EU) competence concerning the Convention on Preventing Violence Against Women and Domestic Violence, commonly known as the Istanbul Convention. The court expressed the view that the EU can enter international treaties independently, even in areas where the EU has shared competencies. In other words, the EU can sign treaties in areas without exclusive competence. Furthermore, Professor Nakanishi evaluates the court opinion, suggesting the possibility of concluding mixed agreements where not all EU member states participate. As a result, this possibility may increase the number of ratifications of similar treaties.