  We study the global forms of class $\mathcal{S}[A_{N-1}]$ 4d $\mathcal{N} =
2$ theories by deriving their defect groups (charges of line operators up to
screening by local operators) from Coulomb branch data. Specifically, we employ
an explicit construction of the BPS quiver for the case of full regular
punctures to show that the defect group is $(\mathbb{Z}_N)^{2g}$, where $g$ is
the genus of the associated Riemann surface. This determines a sector of
surface operators in the 5d symmetry TFT. We show how these can also be
identified from dimensional reduction of M-theory.
