Edit and create seem to more or less work (including selection of the parent). Delete is pending.

lib/models/namespaces.js

@@ -46,6 +46,14 @@ async function updateWithConsistencyCheck(ns) {
             throw new interoperableErrors.ChangedError();
         }
 
+        let iter = ns;
+        while (iter.parent != null) {
+            iter = await tx('namespaces').where('id', iter.parent).first();
+            if (iter.id == ns.id) {
+                throw new interoperableErrors.LoopDetectedError();
+            }
+        }
+
         await tx('namespaces').where('id', ns.id).update(filterObject(ns, allowedUpdateKeys));
     });
 }