The aim of this contribution is to identify the extent
to which an arbitral award can affect third parties’ interests, even though one
is also taught that res judicata is relative and presupposes that the parties
are identical. A distinction must in this respect be made between relative
effect of res judicata, and the possibility of an award affecting third
parties. Once this distinction is made, various procedural mechanisms are suggested
in order to protect the interests of parties and of third parties: the
availability of third party opposition in international arbitration, defining
the interest which may allow such third party opposition, and which limits of
mutual representation may contain this.