But you need a BV provider anyways, right? This is provided by your Java EE 6 server. Which server are you using? If it e.g. is JBoss AS, Glassfish or WebLogic, Hibernate Validator will be the implementation, so you can make use of the HV custom constraints out of the box (if required declare HV as provided dependency for your build so you have the constraints avaiable for compilation, the container will provide the library at runtime).

If you are using a Java EE server which comes with another BV provider, you either might check whether you can switch the BV provider or you just add Hibernate Validator as is to your deployment. BV can work with several providers, so you might want to enforce a specific implementation by e.g. configuring the default provider in META-INF/validation.xml.