  In the framework of perturbation theory, it is possible to put chiral gauge
theories on the lattice without violating the gauge symmetry or other
fundamental principles, provided the fermion representation of the gauge group
is anomaly-free. The basic elements of this construction (which starts from the
Ginsparg-Wilson relation) are briefly recalled and the exact cancellation of
the gauge anomaly, at any fixed value of the lattice spacing and for any
compact gauge group, is then proved rigorously through a recursive procedure.
