  We consider the non-equilibrium dynamics in isolated systems, described by
quantum field theories (QFTs). After being prepared in a density matrix that is
not an eigenstate of the Hamiltonian, such systems are expected to relax
locally to a stationary state. In a presence of local conservation laws, these
stationary states are believed to be described by appropriate generalized Gibbs
ensembles. Here we demonstrate that in order to obtain a correct description of
the stationary state, it is necessary to take into account conservation laws
that are not (ultra-)local in the usual sense of QFT, but fulfil a
significantly weaker form of locality. We discuss implications of our results
for integrable QFTs in one spatial dimension.
