This article argues for a new analysis of Rizzi's (1986) Chain Condition effects, which accounts for the absence of such effects in some derivations. Under the proposed analysis, each moved phrase must be unambiguously linked with its copy at LF. Otherwise, a lethal ambiguity arises, and the derivation crashes. The syntactic position (address) and the numeration index of an A-moved phrase are used to link it with its copy. Long A-movement across another DP can arise in two ways: via an EPP-driven derivation that gives rise to a lethal ambiguity, and via a Case-driven derivation that does not.