Expand on ACL issues

docs/notes/infrastructure/s3-cross-account-transfer.md

@@ -1,5 +1,5 @@
 ---
-title: Cross-account data transfer
+title: Cross-account data transfer in S3
 tags:
   - AWS
 sources:
@@ -49,11 +49,14 @@ To copy bucket contents from a bucket in account A to a bucket in account B:
 
 Now, you can run `aws s3 sync` as the account in account B, and access both buckets.
 
-!!! warning
-     Whilst it might seem counter-intuitive, a **pull**-based transfer is significantly simpler than a **push**-based transfer. Notably, it avoids [issues](https://stackoverflow.com/a/63804619) with ownership issues and ACLs.
+## ACLs
 
-     These can be solved by overwriting the file's ACLs to enforce the bucket owner owns the file:
+Whilst it might seem counter-intuitive, a **pull**-based transfer is significantly simpler than a **push**-based transfer. Notably, it avoids [issues](https://stackoverflow.com/a/63804619) with ownership issues and ACLs. Bucket policies don't seem to apply if the object is owned by a different account, which is the case when ACLs are enabled and the object is written by a user not in the organisation (hence pull-based being best).
 
-     ```
-     aws s3 cp --recursive 's3://<destination_bucket>` 's3://<destination_bucket>` --acl bucket-owner-full-control --metadata-directive REPLACE
-     ```
+These can be solved by overwriting the file's ACLs to enforce the bucket owner owns the file:
+
+```
+aws s3 cp --recursive 's3://<destination_bucket>` 's3://<destination_bucket>` --acl bucket-owner-full-control --metadata-directive REPLACE
+```
+
+It's then good practice to make sure the ACLs are as you expect (eg [`./manage.py fix_document_acls`](https://github.com/torchbox/wagtail-storages?tab=readme-ov-file#django-admin-fix_document_acls)).