  In this paper, we discuss how gauging one-form symmetries in Chern-Simons
theories is implemented in an A-twisted topological open string theory. For
example, the contribution from a fixed H/Z bundle on a three-manifold M,
arising in a BZ gauging of H Chern-Simons, for Z a finite subgroup of the
center of H, is described by an open string worldsheet theory whose bulk is a
sigma model with target a Z-gerbe (a bundle of one-form symmetries) over T^* M,
of characteristic class determined by the H/Z bundle. We give a worldsheet
picture of the decomposition of one-form-symmetry-gauged Chern-Simons in three
dimensinos, and we describe how a target-space constraint on bundles arising in
the gauged Chern-Simons theory has a natural worldsheet realization. Our
proposal provides examples of the expected correspondence between worldsheet
global higher-form symmetries, and target-space gauged higher-form symmetries.
