Institutions,Forum Shopping,and Trade Disputes 741 Steinberg concurs,arguing that the importance of a ruling "lies not only in its implications for the national measures that are the subject of the decision,but also in its precedential value."2 Bhala,in a series of seminal articles on the subject,4 calls this de facto stare decisis,which,in contrast to de jure stare decisis,is fol- lowed for extra-and quasi-legal factors,including custom and habit,rather than as a matter of legal requirement.25 Importantly,Bhala argues that de facto and de jure stare decisis are both "binding"sources of law,in that they establish a pre- sumption that precedents will be followed in the future.6 The Appellate Body (AB)bears out this view,arguing in a highly important ruling that"[t]he reason- ing in our Report in United States-Shrimp on which the Panel relied was not dicta;it was essential to our ruling.The Panel was right to use it,and right to rely on it.Nor are we surprised that the panel made frequent references to our Report in United States-Shrimp.Indeed,we would have expected the Panel to do so."27 NAFTA panels similarly follow a de facto stare decisis,as in the safeguards dis- pute over Mexican broom corn brooms,where the institution's prior ruling in Canada-Agricultural Tariffs was central in this case.28 Equally telling,these bod- ies of jurisprudence are well known and,at the multilateral level,meticulously catalogued in the WTO Analytical Index,which identifies the key precedents per- taining to each agreement,setting out,for example,that the AB's ruling in Canada- Autos is the relevant case law in distinguishing a de facto from a de jure subsidy. In short,as Bhala concludes,it is only "[o]ur intellectual rigidity [that]precludes us from admitting openly that the holdings of the Appellate Body-and,for that matter,panel-reports actually are a source of international law."30 Since de facto stare decisis is followed for extra-and quasi-legal reasons,includ- ing custom and habit,and not as a matter of legal requirement,it could be argued that precedents from one institution might constrain or shape the rulings of another, making it hard to disentangle different bodies of jurisprudence,and thus to engage in forum shopping.This concern is unwarranted,both in theory and in practice. For its part,the WTO has not cited a single ruling by NAFTA(or any other regional institution),3!not least because not all WTO members are NAFTA members,and thus are not bound by the precedents of this institution.This logic comes to the fore in Argentina-Poultry Antidumping Duties,for example,where the panel found Mercosur's ruling irrelevant to its deliberations.Building on the AB's ruling in 23.Steinberg 2004,254. 24.Bhala2001,1999b,and1999a. 25.Bhala1999b,3-4. 26.Ibid,9. 27.WTO Doc.WT/DS58/AB/RW,para.107.All WTO documents are available at(http://www. wto.org).Accessed 12 June 2007. 28.NAFTA Doc.USA-97-2008-01,para.44. 29.WT02003. 30.Bhala1999a,850-51. 31.In my effort to survey WTO reports and trade law experts on citations to NAFTA case law, I was unable to turn up a single example.Steinberg concurs, arguing that the importance of a ruling “lies not only in its implications for the national measures that are the subject of the decision, but also in its precedential value+”23 Bhala, in a series of seminal articles on the subject, 24 calls this de facto stare decisis, which, in contrast to de jure stare decisis, is fol￾lowed for extra- and quasi-legal factors, including custom and habit, rather than as a matter of legal requirement+ 25 Importantly, Bhala argues that de facto and de jure stare decisis are both “binding” sources of law, in that they establish a pre￾sumption that precedents will be followed in the future+ 26 The Appellate Body ~AB! bears out this view, arguing in a highly important ruling that “@t#he reason￾ing in our Report in United States—Shrimp on which the Panel relied was not dicta; it was essential to our ruling+ The Panel was right to use it, and right to rely on it+ Nor are we surprised that the panel made frequent references to our Report in United States—Shrimp+ Indeed, we would have expected the Panel to do so+”27 NAFTA panels similarly follow a de facto stare decisis, as in the safeguards dis￾pute over Mexican broom corn brooms, where the institution’s prior ruling in Canada—Agricultural Tariffs was central in this case+ 28 Equally telling, these bod￾ies of jurisprudence are well known and, at the multilateral level, meticulously catalogued in the WTO Analytical Index, which identifies the key precedents per￾taining to each agreement, setting out, for example, that the AB’s ruling in Canada— Autos is the relevant case law in distinguishing a de facto from a de jure subsidy+ 29 In short, as Bhala concludes, it is only “@o#ur intellectual rigidity @that# precludes us from admitting openly that the holdings of the Appellate Body—and, for that matter, panel—reports actually are a source of international law+”30 Since de facto stare decisis is followed for extra- and quasi-legal reasons, includ￾ing custom and habit, and not as a matter of legal requirement, it could be argued that precedents from one institution might constrain or shape the rulings of another, making it hard to disentangle different bodies of jurisprudence, and thus to engage in forum shopping+ This concern is unwarranted, both in theory and in practice+ For its part, the WTO has not cited a single ruling by NAFTA ~or any other regional institution!, 31 not least because not all WTO members are NAFTA members, and thus are not bound by the precedents of this institution+ This logic comes to the fore in Argentina—Poultry Antidumping Duties, for example, where the panel found Mercosur’s ruling irrelevant to its deliberations+ Building on the AB’s ruling in 23+ Steinberg 2004, 254+ 24+ Bhala 2001, 1999b, and 1999a+ 25+ Bhala 1999b, 3–4+ 26+ Ibid+, 9+ 27+ WTO Doc+ WT0DS580AB0RW, para+ 107+ All WTO documents are available at ^http:00www+ wto+org&+ Accessed 12 June 2007+ 28+ NAFTA Doc+ USA-97-2008-01, para+ 44+ 29+ WTO 2003+ 30+ Bhala 1999a, 850–51+ 31+ In my effort to survey WTO reports and trade law experts on citations to NAFTA case law, I was unable to turn up a single example+ Institutions, Forum Shopping, and Trade Disputes 741