diff --git a/src/backend/InvenTree/order/api.py b/src/backend/InvenTree/order/api.py
index d6b66ae4c4..eed3f866eb 100644
--- a/src/backend/InvenTree/order/api.py
+++ b/src/backend/InvenTree/order/api.py
@@ -64,6 +64,7 @@ from order.status_codes import (
 )
 from part.models import Part
 from users.models import Owner
+from users.permissions import check_user_permission
 
 
 class GeneralExtraLineListOutputOptions(OutputConfiguration):
@@ -2386,6 +2387,32 @@ class OrderCalendarExport(ICalFeed):
     timezone = settings.TIME_ZONE
     file_name = 'calendar.ics'
 
+    # Map the URL 'ordertype' kwarg to the corresponding order model,
+    # so that access can be checked against the matching RuleSet
+    ORDER_MODELS = {
+        'purchase-order': models.PurchaseOrder,
+        'sales-order': models.SalesOrder,
+        'return-order': models.ReturnOrder,
+        'transfer-order': models.TransferOrder,
+    }
+
+    def check_permission(self, request, **kwargs):
+        """Check that the requesting user has 'view' permission for the requested order type.
+
+        Returns a 403 JsonResponse if the user lacks the required RuleSet permission,
+        or None if access is permitted.
+        """
+        model = self.ORDER_MODELS.get(kwargs.get('ordertype'))
+
+        if model is not None and not check_user_permission(request.user, model, 'view'):
+            response = JsonResponse({
+                'detail': 'You do not have permission to view this resource.'
+            })
+            response.status_code = 403
+            return response
+
+        return None
+
     def __call__(self, request, *args, **kwargs):
         """Overload call in order to check for authentication.
 
@@ -2402,6 +2429,8 @@ class OrderCalendarExport(ICalFeed):
 
         if request.user.is_authenticated:
             # Authenticated on first try - maybe normal browser call?
+            if forbidden := self.check_permission(request, **kwargs):
+                return forbidden
             return super().__call__(request, *args, **kwargs)
 
         # No login yet - check in headers
@@ -2420,6 +2449,8 @@ class OrderCalendarExport(ICalFeed):
         # Check again
         if request.user.is_authenticated:
             # Authenticated after second try
+            if forbidden := self.check_permission(request, **kwargs):
+                return forbidden
             return super().__call__(request, *args, **kwargs)
 
         # Still nothing - return Unauth. header with info on how to authenticate
diff --git a/src/backend/InvenTree/order/test_api.py b/src/backend/InvenTree/order/test_api.py
index 28ee156c1e..418bb1e1c2 100644
--- a/src/backend/InvenTree/order/test_api.py
+++ b/src/backend/InvenTree/order/test_api.py
@@ -853,6 +853,21 @@ class PurchaseOrderTest(OrderTest):
         )
         self.assertEqual(response.status_code, 200)
 
+    def test_po_calendar_no_permission(self):
+        """Test that an authenticated user without purchase_order view permission is denied."""
+        self.clearRoles()
+
+        response = self.get(
+            reverse('api-po-so-calendar', kwargs={'ordertype': 'purchase-order'}),
+            expected_code=403,
+            format=None,
+        )
+
+        resp_dict = response.json()
+        self.assertEqual(
+            resp_dict['detail'], 'You do not have permission to view this resource.'
+        )
+
     def test_po_custom_status_query_count(self):
         """Test that listing PurchaseOrders with custom statuses does not cause N+1 queries.
 
@@ -2111,6 +2126,21 @@ class SalesOrderTest(OrderTest):
         self.assertGreaterEqual(n_events, 1)
         self.assertEqual(number_orders_incl_complete, n_events)
 
+    def test_so_calendar_no_permission(self):
+        """Test that an authenticated user without sales_order view permission is denied."""
+        self.clearRoles()
+
+        response = self.get(
+            reverse('api-po-so-calendar', kwargs={'ordertype': 'sales-order'}),
+            expected_code=403,
+            format=None,
+        )
+
+        resp_dict = response.json()
+        self.assertEqual(
+            resp_dict['detail'], 'You do not have permission to view this resource.'
+        )
+
     def test_export(self):
         """Test we can export the SalesOrder list."""
         set_global_setting(models.SalesOrder.UNLOCK_SETTING, True)
@@ -3564,6 +3594,21 @@ class ReturnOrderTests(InvenTreeAPITestCase):
         calendar = Calendar.from_ical(response.content)
         self.assertIsInstance(calendar, Calendar)
 
+    def test_ro_calendar_no_permission(self):
+        """Test that an authenticated user without return_order view permission is denied."""
+        self.clearRoles()
+
+        response = self.get(
+            reverse('api-po-so-calendar', kwargs={'ordertype': 'return-order'}),
+            expected_code=403,
+            format=None,
+        )
+
+        resp_dict = response.json()
+        self.assertEqual(
+            resp_dict['detail'], 'You do not have permission to view this resource.'
+        )
+
     def test_export(self):
         """Test data export for the ReturnOrder API endpoints."""
         # Export return orders
@@ -4114,6 +4159,21 @@ class TransferOrderTest(OrderTest):
         self.assertGreaterEqual(n_events, 1)
         self.assertEqual(number_orders_incl_complete, n_events)
 
+    def test_transfer_order_calendar_no_permission(self):
+        """Test that an authenticated user without transfer_order view permission is denied."""
+        self.clearRoles()
+
+        response = self.get(
+            reverse('api-po-so-calendar', kwargs={'ordertype': 'transfer-order'}),
+            expected_code=403,
+            format=None,
+        )
+
+        resp_dict = response.json()
+        self.assertEqual(
+            resp_dict['detail'], 'You do not have permission to view this resource.'
+        )
+
     def test_export(self):
         """Test we can export the TransferOrder list."""
         n = models.TransferOrder.objects.count()