  It is shown that certain global obstructions to gauge-invariance in chiral
gauge theory, described in the continuum by Alvarez-Gaume and Ginsparg, are
exactly reproduced on the lattice in the Overlap formulation at small non-zero
lattice spacing (i.e. close to the classical continuum limit). As a
consequence, the continuum anomaly cancellation condition $d_R^{abc}=0$ is seen
to be a necessary (although not necessarily sufficient) condition for anomaly
cancellation on the lattice in the Overlap formulation.
