/errors/campaign_criterion_error.proto 

--- v23/errors/campaign_criterion_error.proto   2026-06-18 21:38:47.000000000 +0000
+++ v24/errors/campaign_criterion_error.proto   2026-06-18 21:38:53.000000000 +0000
@@ -134,5 +134,9 @@

     // Video lineup ID does not exist.
     INVALID_VIDEO_LINEUP_ID = 28;
+
+    // For Local Services PMax campaigns, at least one positive location
+    // criterion must remain.
+    CANNOT_REMOVE_ALL_LOCATIONS_FROM_LOCAL_SERVICES_PMAX_CAMPAIGN = 29;
   }
 }