I doubt that most states prohibit burying pet ashes inside a human’s casket or ash-urn. You can bury a person with any inanimate objects — rosaries, photos, etc.; young children are often buried with a favorite stuffed animal. While I expect most if not all states either prohibit or have tight restrictions on uncremated pets being buried with their humans, I don’t think most pay any attention at all to what’s tucked into a casket, or whether there are more ashes than just the human’s in the urn that’s buried.