  A theory of electromagnetism is proposed that is based on the Fermi
Lagrangian, which is symmetric under electromagnetic spin rotation. Its
features are: - the four-potential is unambiguously determined by the
inhomogeneous wave equation and boundary conditions at infinity. - the Lorenz
condition and minimal coupling then follow from charge conservation. -
electromagnetic spin is conserved and spin operators can be defined without
sacrificing covariance. - quantisation is fully covariant, without redefining
the metric. - all experimental predictions are the same as in the standard
theory. This result proves that electromagnetic gauge invariance is redundant
as a fundamental principle of physics.
