  Light propagation in random media is notorious for its resilience to
(Anderson) wave localization. We here argue that in materials with slow
helicity relaxation previously unnoticed principles of topology reinforce
delocalization. We show that the effective electromagnetic action is governed
by principles, identical to those protecting delocalization at topological
insulator surface states. The length scales over which these exert a protective
influence depend on the conservation of helicity, leading to the prediction
that light scattering in media with, e.g., strong magnetic and electric dipolar
resonances evades localization over large scales.
