  We revisit acceleration-induced nonlocal electrodynamics and the phenomenon
of photon spin-rotation coupling. The kernel of the theory for the
electromagnetic field tensor involves parity violation under the assumption of
linearity of the field kernel in the acceleration tensor. However, we show that
parity conservation can be maintained by extending the field kernel to include
quadratic terms in the acceleration tensor. The field kernel must vanish in the
absence of acceleration; otherwise, a general dependence of the kernel on the
acceleration tensor cannot be theoretically excluded. The physical implications
of the quadratic kernel are briefly discussed.
