  The issue of the BRST symmetry in presence of the Gribov horizon is addressed
in Euclidean Yang-Mills theories in the Landau gauge. The positivity of the
Faddeev-Popov operator within the Gribov region enables us to convert the soft
breaking of the BRST invariance exhibited by the Gribov-Zwanziger action into a
non-local exact symmetry, displaying explicit dependence from the
non-perturbative Gribov parameter. Despite its non-locality, this symmetry
turns out to be useful in order to establish non-perturbative Ward identities,
allowing us to evaluate the vacuum expectation value of quantities which are
BRST exact. These results are generalized to the refined Gribov-Zwanziger
action introduced in [1], which yields a gluon propagator which is
non-vanishing at the origin in momentum space, and a ghost propagator which is
not enhanced in the infrared.
