  It is shown that physical states of a non-abelian Yang-Mills-Higgs dyon are
invariant under large gauge transformations that do not commute with its
magnetic field. This result is established within an enlarged Hamiltonian
formalism where surface terms are kept as dynamical variables. These additional
variables are parameters of large gauge transformations, and are potential
collective coordinates for the quantization of the monopole. Our result implies
that there are no physical effects associated to some large gauge
transformations and therefore their parameters should not be counted as
collective coordinates.
