An
arbitrator in an international arbitration, when applying a national law
(whether chosen by the parties or identified by him), may be confronted with a
conflict in the hierarchy of norms within that national law, for example where
one of the parties argues that the substantive rule applicable to the matter is
contrary to the constitution of the State in question, or to a treaty there in
force, or to a European regulation that should be taken into account. This
article studies the nature of such a conflict as it appears to the arbitrator,
searches for the general principle that should guide the arbitrator seeking to address
the conflict and considers the hypotheses that should be distinguished in order
to apply this general principle.