  In this paper we study three-dimensional orbifolds by 2-groups with a
trivially-acting one-form symmetry group BK. These orbifolds have a global
two-form symmetry, and so one expects that they decompose into (are equivalent
to) a disjoint union of other three-dimensional theories, which we demonstrate.
These theories can be interpreted as sigma models on 2-gerbes, whose formal
structures reflect properties of the orbifold construction.
