diff --git a/backend/app/routers/events.py b/backend/app/routers/events.py
index 140d046..e7bd57f 100644
--- a/backend/app/routers/events.py
+++ b/backend/app/routers/events.py
@@ -353,7 +353,9 @@ async def update_event(
         update_data["recurrence_rule"] = json.dumps({k: v for k, v in rule_obj.items() if v is not None}) if rule_obj else None
 
     # SEC-04: if calendar_id is being changed, verify the target belongs to the user
-    if "calendar_id" in update_data and update_data["calendar_id"] is not None:
+    # Only verify ownership when the calendar is actually changing — members submitting
+    # an unchanged calendar_id must not be rejected just because they aren't the owner.
+    if "calendar_id" in update_data and update_data["calendar_id"] is not None and update_data["calendar_id"] != event.calendar_id:
         await _verify_calendar_ownership(db, update_data["calendar_id"], current_user.id)
 
     # M-01: Block non-owners from moving events off shared calendars
diff --git a/frontend/src/components/calendar/EventDetailPanel.tsx b/frontend/src/components/calendar/EventDetailPanel.tsx
index f7ee3ff..0fe4b34 100644
--- a/frontend/src/components/calendar/EventDetailPanel.tsx
+++ b/frontend/src/components/calendar/EventDetailPanel.tsx
@@ -392,8 +392,8 @@ export default function EventDetailPanel({
   // --- Handlers ---
 
   const handleEditStart = async () => {
-    // For shared events, acquire lock first (owners skip locking)
-    if (isSharedEvent && myPermission !== 'owner' && event && typeof event.id === 'number') {
+    // For shared events, acquire lock first
+    if (isSharedEvent && event && typeof event.id === 'number') {
       try {
         await acquireLock();
         setLockInfo(null);