  It is shown how to break the symmetry of a Lagrangian with duality symmetry
between electric and magnetic monopoles, so that at low energy, electric
monopole interactions continue to be observed but magnetic monopole
interactions become very highly suppressed to the point of effectively
vanishing. The "zero-charge" problem of source-free electrodynamics is solved
by requiring invariance under continuous, local, duality transformations, while
local duality symmetry combined with local U(1)EM gauge symmetry leads
naturally and surprisingly to an SU(2)D duality gauge group.
