  We present a novel interpretation of the Wigner-Araki-Yanase (WAY) theorem
based on a relational view of quantum mechanics. Several models are analysed in
detail, backed up by general considerations, which serve to illustrate that the
moral of the WAY theorem may be that in the presence of symmetry, a measuring
apparatus must fulfil the dual purpose of both reflecting the statistical
behaviour of the system under investigation, and acting as a physical reference
system serving to define those quantities which must be understood as relative.
