 The principle of the common cause can be derived within the context of deterministic laws. Yet deterministic laws also appear to undercut the time-asymmetry of common cause inferences. Under determinism, if there is an event C in the past of two events A and B that screens A and B off from each other, then there will also be an event C* taking place after A and B that occurs exactly if C occurs and that renders the two events conditionally independent (Arntzenius 1992). In reply to this worry one can argue that future screening-off events, unlike those in the past, will in general be highly non-natural and non-localized (Woodward 2007). Demanding that appropriate physical variables represent localized and not highly gerrymandered events allows us to preserve the asymmetry induced by the initial randomness assumption.