  We show that the first moment of the spin-dependent structure function
$g_1^{\gamma}(x,Q^2)$ of a real photon vanishes independent of the momentum
transfer $Q^2$ it is probed with. This result is non-perturbative: it holds to
all orders in perturbation theory in abelian and non-abelian gauge theory and
at every twist.

High Energy Physics - Phenomenology