Mixing is optional only when an international agreement concerns exclusive and non-exclusive EU competences. In this case, it can be concluded exclusively by the Union or, failing that, jointly by the Union and the Member States.5 This type of optional mix applies regardless of whether the Union`s non-exclusive competence is of a common or assistance nature. In terms of support for competences, both the Union and the Member States retain their power of action independently of the agreements reached by the other party. If the objective of an international agreement is therefore a matter of the Union`s support competence, for example in the area of health policy, the Union has the right to conclude it jointly with the Member States. However, the Union could also choose to relinquish its supporting powers, or even be obliged to do so under the principle of subsidiarity.6 If issues governed by an international agreement (P.184) fall within the shared competence and exclusive competence of the Member States, mixing is also optional. However, in such a case, Member States would be allowed to conclude the agreement without the Union if it decided not to activate its powers. If, despite the best efforts of Member States in an area of shared competence, no common position is adopted, the following should be considered. Since the issues relating to such a case fall within the competence of the Union, even in the absence of a common position, 125 loyalties remain in place in order to preserve certain interests of the Union and the general interest of the Union for the unity of international representation. This means that Member States must take due account of the relevant interests of the Union, even if they have not been expressed by a Council decision or as an EU strategy. In addition, the loyalty mandates that divide the EU Member States in defining a negotiating position126 will also be more determined to this commitment when the jurisdictional situation (p.202) or the agreement itself is interdependent/complex. As has already been mentioned, MOX Plant can be seen as the basis for a general obligation in the area of joint agreements to “inform and consult with Community institutions before participating in individual measures” 127 A joint agreement refers to an agreement – for example, an agreement that also deals with regulatory or investment issues – between the EU and a third country, which deals with both the competences and competences of the EU and those reserved exclusively for EU Member States.