In this paper, I explore the unexpected consequences of Weibo’s geographic tagging policy in China, a case study that offers broader insights into information control in authoritarian regimes. Intended to “Build a National Wall” against overseas influence, this policy inadvertently created “Provincial Walls” within the country. Using unique high-frequency panel data from 200 influential Weibo accounts and a data leakage incident, coupled with a rigorous methodological approach, I demonstrate that the policy effectively reduces public discourse and regime-threatening information. However, it does so not by suppressing overseas users but by deterring domestic users from engaging in out-of-province discussions. This policy also has unintended effects, such as strengthening local identities, which can intensify geo-group division at the expense of national cohesion, and heighten cross-provincial conflict, potentially exacerbating social tensions. These findings reveal the complex impacts of user tagging policies in authoritarian regimes. While they may offer short-term benefits in controlling information, they can also create long-term challenges by aggravating the dictator’s informational dilemma and fostering conditions conducive to collective action.