You are the object owner or you have the permission to write the object ACL.
An object owner is the account that uploads the object, but may not be the owner of the bucket that stores the object. For example, account B is granted the permission to access a bucket of account A, and account B uploads a file to the bucket. In that case, account B, instead of the bucket owner account A, is the owner of the object. By default, account A is not allowed to access this object and cannot read or modify the object ACL.
ACL permissions for encrypted objects cannot be granted to registered users or anonymous users.
Enter an account ID or account name and specify ACL permissions for the account. You can obtain the account ID or account name from the My Credentials page. The account ID and account name correspond to the Domain ID and Domain Name respectively on the My Credentials page.