  We study the plaquette valence bond solid phase in a XXZ type spin-1/2 model
in the kagome lattice. The low energy theory for this phase is a U(1) lattice
gauge theory on the honeycomb lattice. We find that there is an emergent 1-form
U(1) symmetry in low energy, and there is a mixed anomaly. We also show that
this 1-form symmetry constraints the longitudinal dynamical structure factor
and leads to the selection rule relating to the vanishing intensity along some
high symmetry momentum paths (e.g. $\Gamma-M$ path). We point out that this
emergent 1-form symmetry is robust against the translation symmetry preserving
UV perturbation, thus the selection rule will also apply to the model which is
obtained by perturbing the classical limit of our model.
