The issue of the sale of Maltese citizenship to foreign investors or the so-called “citizenship investment scheme” raises concerns in the European Union and its member states. These fears, although to some extent justified, but the legality of taking legal action against Malta must be examined, and this must be done in light of both the law International and the EU law. The reason for doing the above-mentioned examination under the international law is because the relationship between Malta and the European Union at the international level is a relationship between a state and an international organization governed by international law, not to mention the role of the international law in the emergence and the development of the European Union. Also one of the major arguments of the Union is that, the action of Malta is against the principles of international law about states' nationality. And as for European law, the relationship between the European Union and Malta is a union's relationship with a member state governed by the founding treaties of the Union, that resembles the constitution in some ways, and regulates their relationship between them, and defines their competencies. This is what we will address in this research.