The external conflict in Breaking Dawn has to do with the Volturri who are the enforcers of vampire laws. When Irina--a cousin of the Cullens misinterprets what she sees when see observes Renesmee, the child of Edward and Bella, she goes to the Volturri claiming they created an immortal child. Immortal children were against the law because vampires are not supposed to call attention to themselves and vampire children are impossible to control. Therefore, the conflict has to do with the Volturri trying to enforce vampire law by killing Renesmee and the Cullen clan while the Cullens must prove that Renesmee is actually a half-human and half-vampire child who poses no threat to vampire culture.They gather other vampire witnesses to attest that Renesmee is no threat and to stand with them against the Volturri.