The allocation of responsibility for violations of international law is critical to that system's effectiveness and credibility. The central claim of this study is that international law requires States (and, under certain circumstances, other entities) to be held answerable for their acts and omissions that cause or otherwise contribute to trafficking. The scant attention paid to State responsibility in the legal literature on trafficking suggests that this aspect of law is of marginal, perhaps only historical importance. This is both a legal and strategic mistake. Certainly, formal recourse to doctrines of State responsibility through international courts and tribunals is relatively uncommon. Such recourse is expensive, time-consuming, and often not seen to be in the long-term interests of even those States directly affected by a breach of legal obligation. It is to be expected that the development of treaty regimes establishing supervisory mechanisms and compliance procedures will further lessen the perceived need for formal invocation of responsibility.