I have to say that this is not a good practice, mixing query and persistence stuffs inside business rules, but sure you can do it. Is a matter of inserting the hibernate session in the KieSession, and then call the hibernate session methods inside your rules. It's typical used together with the "from" clause of drools, i order to consider Entities in rules. Read this article [1] that has some ideas. It's related to drools 5, but should work in the same way with drools 6.

[1] http://magazine.redhat.com/2008/07/11/jboss-drools-meets-hibernate/