The propagation of a neutral massless particle with anomalous magnetic
moment in an external electromagnetic field is considered in both pse
udoclassical and quantum mechanics. The quantum description employs a
Hamiltonian in the Foldy-Wouthuysen representation. This Hamiltonian i
s obtained by applying the Weyl quantization scheme to the pseudoclass
ical Hamiltonian of a massive charged particle having an anomalous mag
netic moment and interacting with an external electromagnetic field.