  The abelian Chern-Simons theory is perturbed by introducing local
gauge-invariant interaction terms depending on the curvature. The computation
of the correlation function of two Wilson lines for two smooth closed
nonintersecting curves is reported up to four loops and is shown to be
unaffected by radiative corrections. This result ensures the stability of the
linking number of the two curves with respect to the local perturbations which
may be added to the Chern-Simons action.
