Amazon S3 Replication adds support for two-way replication

Amazon S3 Replication now gives you the flexibility of replicating object metadata changes for two-way replication between buckets. With this new feature, replica modification sync, you can easily replicate metadata changes like object access control lists (ACLs), object tags, or object locks on the replicated objects. This two-way replication is important if you want to build shared datasets across multiple regions and keep all object and object metadata changes in sync. 

Source:: Amazon AWS