  It is shown that at finite temperature and in the presence of magnetic
sources magnetic fields are screened. This is proven within the framework of
classical transport theory both for the Abelian and non-Abelian plasmas.
Magnetic screening arises in this formalism as a consequence of polarization
effects occurring in the plasmas, and it is proportional to the inverse of the
gauge coupling constant. It is then discussed whether this mechanism could be
relevant in realistic quantum gauge field theories, such as QCD.
