Yes, Seam uses Hibernate Validator directly, it does not need integration with the ORM layer. And then if Hibernate is the underlying EJB3 persistence provider, the constraints are also enforced when writing to/from the database.
Actually it is also possible to integrate HV with other EJB3 persistence providers. We should probably make that integration a standard feature but we did not get around to it yet.
Thanks for the reply, I appreciate all the hard work. BTW, your javaone presentation was extremely entertaining.