On the face of it, most ASEAN external agreements present themselves as plurilateral agreements. The parties to such agreements are a minimum number, if not all, of ASEAN Member States and any number of third states. In the large majority of cases, the language of ASEAN external agreements is seemingly clear-cut and speaks, for example, of ‘[a]n agreement between ASEAN Member States and the Republic of Korea (ROK) on Forestry Cooperation’. At times, to meet any remaining doubt, some external agreements specify further. For example, Article 3 Agreement Establishing the ASEAN-Australia-New Zealand Free Trade Area (AANZFTA) provides that ‘[p]arties means the ASEAN Member States, Australia and New Zealand collectively; … [p]arty means an ASEAN Member State or Australia or New Zealand’. ASEAN as an IO is obviously not a party to the agreement.

The fact that in some instances the ASEAN Secretary-General also signs such agreements is immaterial if such agreements are read as traditional plurilateral agreements. On this reading, varieties of the formula that refers to ASEAN as a collectivity do not detract from the plainly plurilateral nature of the agreements. Where ASEAN is referred to as a collectivity, this may be understood to be an umbrella term or shorthand for the individual Member States. This means that it is the governments of the respective ASEAN Member States who conclude the agreement rather than ASEAN as an institutional entity. That they collectively form ASEAN is inconsequential with regard to the nature of the external instrument as a plurilateral agreement. Where the present type of external agreements is concerned, ASEAN as an IO is sidelined. At the most, it provides a forum for treaty making by its Member States, or it serves as a venue for coordination. As plurilateral agreements, the internal effects of ASEAN external agreements are equal to the effects within ASEAN Member States of any other international agreement.

The internal effects of ASEAN external agreements may of course differ in light of the nature of the agreement and in view of the specific obligations that such agreements create for Member States. Salient points to consider include whether agreements require that Member States bring their domestic legislation in conformity, whether the existence of contrary legislation itself triggers state responsibility, whether obligations set out in international agreements are sufficiently precise, or whether complainants can seek redress or relief from international dispute settlement mechanisms.