Compactifications of the Chaudhuri-Hockney-Lykken (CHL) string to eight dimensions can be characterized by embeddings of root lattices into the rank 12 momentum lattice ${\Lambda }_M$, the so-called Mikhailov lattice. Based on these data, we devise a method to determine the global gauge group structure including all $U\left(1\right)$ factors. The key observation is that, while the physical states correspond to vectors in the momentum lattice, the gauge group topology is encoded in its dual. Interpreting a nontrivial ${\pi }_1\left(G\right)\equiv Z$ for the non-Abelian gauge group $G$ as having gauged a $Z$ 1-form symmetry, we also prove that all CHL gauge groups are free of a certain anomaly [1] that would obstruct this gauging. We verify this by explicitly computing $Z$ for all 8D CHL vacua with $\mathrm{rank}\left(G\right)=10$. Since our method applies also to $T^2$ compactifications of heterotic strings, we further establish a map that determines any CHL gauge group topology from that of a “parent” heterotic model.