We study the symmetry of Maxwell's equations for external moving media together with the additional Minkowski constitutive equations (or Maxwell–Minkowski equations). We established that the system is conformally invariant.
Ivan Tsyfra. "Symmetry of the Maxwell and Minkowski Equations System." J. Geom. Symmetry Phys. 9 75 - 81, 2007. https://doi.org/10.7546/jgsp-9-2007-75-81