# Faddeev-Popov Ghosts in the canonical formalism

In the Lorenz gauge in electrodynamics, the timelike and longitudinal components can be eliminated by prescribing the Gupta-Bleuler condition $\partial^{\mu}A_{\mu}|\Psi)$ on physical states. This gives a condition $\square\Lambda=0$ on gauge transformations. In a similar fashion, is it possible to derive the Faddeev-Popov ghosts and the ghost Lagrangian in the canonical formalism in such a way that Lorentz invariance is maintained?