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OSIPP基幹講座教員の2月の研究業績をご紹介します。 ・前川和歌子 先生　・髙田陽奈子 先生　・二杉健斗 先生　・松島法明 先生　・西山克彦先生 Wakako Maekawa, Hinako Takata（論文）"External Influence on Latin America’s ‘Peace-Versus-Justice’Dilemma: (How) Do Inter-American Court of Human Rights Anti-Amnesty Law Judgments Affect Peace and National Reconciliation?"International Journal of Transitional Justice, 24 February 2026(査読有)DOI: https://doi.org/10.1093/ijtj/ijag004Abstract: Judgments of the Inter-American Court of Human Rights (IACtHR) that hold amnesty laws illegal under the American Convention on Human Rights (‘anti-amnesty law judgments’) have often been criticized for excessively prioritizing human rights and justice over peace and national reconciliation. This study empirically examines how the IACtHR should address this ‘peace-versus-justice dilemma.’ Using IACtHR judgments from 2003 to 2019 and case studies of Peru and El Salvador, we analyze the impact of the IACtHR’s anti-amnesty law judgments on peace and national reconciliation in Latin American societies, focusing on protests against governments and polarization as early indicators of civil conflict. Our findings suggest that although the IACtHR’s anti-amnesty law judgments do not necessarily undermine peace and national reconciliation directly, the IACtHR should address the resultant long-term political and social polarization as a potential factor in social destabilization that could lead to civil conflict.Wakako Maekawa（論文）Wakako Maekawa and Theodora-Ismene Gizelis"Trading peace for hazard management? peace agreement implementation and United Nations peace operations during natural hazards"World Development, vol.203, 2026-03-19(査読有)doi: https://doi.org/10.1016/j.worlddev.2026.107387Abstract: Although United Nations Peace Operations (UNPOs) can strengthen capacity and improve responses to natural hazards, the core peace operation and ability to produce peace can become victims of crisis management success. Natural hazards can impede UNPOs’ activities and peace accord implementation through three mechanisms: 1) UNPOs activities are diverted to immediate humanitarian assistance, away from core UNPOs’ activities; 2) changes to the bargaining process; and 3) lower opportunity costs of violence and increased opportunities to renege on agreements or call for renegotiations. We compare peace agreement implementation with UNPOs versus peace agreement implementation without UNPOs when facing natural hazards. In an analysis of countries with comprehensive peace agreement implementations between 1992 and 2015 we find that natural hazards during UNPOs deployment see lower subsequent peace agreement implementation relative to hazards in countries without UNPOs. We see these findings as consistent with greater dependency on UNPOs, creating greater tension between responses to natural hazards and peace implementation. Further analysis to unpack the three mechanisms suggests support for the first two mechanisms.二杉健斗 （論文）「国際投資法と持続可能な発展のディスクール――なぜ「調和」の論理が「対立」を生むのか――」世界法年報46号（2026年）162-187頁 概要：世界法学会2025年度研究大会（統一テーマ「国際法における環境法的思考の可能性―持続可能性を統合するグローバルな法システムの課題―」）での報告をもとにした原稿。本稿は、国際投資法と環境保護をめぐる「対立言説」（投資仲裁が環境規制を萎縮させるという批判）と「調和言説」（投資法は正当な規制を尊重し環境と両立するという主張）の緊張関係が生じる原因を、知識社会学・科学社会学の視座を用いて分析した。この対立は、調和言説の法的根拠の欠如でも、批判者側の法的知識の欠如によるものでもなく、むしろ何が「正当」な規制かを決定する権力が投資法側に偏在していることへの異議申立てに起因すると論じている。Noriaki Matsushima（DP）Noriaki Matsushima, Kazuki Nishikawa, Jiaying Qiu “The effects of minimum wage in inter-regional duopoly competition”OSIPP Discussion Paper: DP-2026-E-001, March 24, 2026https://www.osipp.osaka-u.ac.jp/archives/DP/2026/DP2026E003.pdfhttps://hdl.handle.net/11094/104192Abstract: A binding minimum wage can raise the regulated firm's profits when labor-market power interacts with product-market competition. We develop a duopoly model in which firms compete in the same product market but hire workers from distinct, geographically segmented labor markets. Because the minimum wage applies only to one firm's labor market, it does not directly raise its rival's costs. With monopsony power, the minimum wage reduces the regulated firm's marginal cost and induces it to expand output, forcing its rival to contract through strategic interaction. Under Cournot competition, this mechanism also increases total employment and consumer surplus.Katsuhiko Nishiyama（DP）“The Impact of Job Displacement on Health Insurance Status in the post-ACA Era”OSIPP Discussion Paper: DP-2026-E-001, February 27, 2026https://www.osipp.osaka-u.ac.jp/archives/DP/2026/DP2026E001.pdfAbstract: This paper examines whether insurance sources expanded under the Affordable Care Act (ACA), particularly health insurance marketplaces and Medicaid, compensate for the loss of employer-sponsored health insurance (ESHI) following job displacement. Using monthly data from the 2014--2016 Survey of Income and Program Participation, I estimate duration-specific effects of displacement on each coverage source with a difference-in-differences design. ESHI coverage falls by 15 to 18 percentage points within a few months of displacement, with only slight recovery over the following year. Medicaid enrollment increases modestly, driven entirely by workers in expansion states where coverage increases exceed 7 percentage points. Directly purchased private insurance shows no discernible response despite marketplace availability and premium subsidies, and this holds across income levels. These findings indicate that ACA marketplace reforms in the sample period provide limited protection for displaced workers.

OSIPP基幹講座教員の2月の研究業績をご紹介します。 ・中嶋啓雄 先生　・髙田陽奈子 先生　・大久保邦彦 先生　・川窪 悦章 先生　 中嶋啓雄（論文） 「モンロー・ドクトリンの歴史的水脈」『世界』1003号（2026年3 月）、34～39頁https://www.iwanami.co.jp/book/b10159266.html 概要：昨年12月に公表されたアメリカ合衆国の外交・安全保障の基本方針「国家安全保障戦略」で掲げられたモンロー・ドクトリンのトランプ系論（コロラリー）、いわゆるドンロー主義を背景とした、年始の米軍介入によるベネズエラのマドゥロ大統領拘束を受けて、モンロー・ドクトリンに基づくアメリカの中南米への介入の歴史、また、モンロー・ドクトリンと国際法・国際機関との関係等を論じた。 Hinako Takata （単著） Pluralising Actors and Norms in Human Rights Treaties: Beyond Monolithic States (Hart Publishing, 2026)、査読有https://www.bloomsbury.com/us/pluralising-actors-and-norms-in-human-rights-treaties-9781509984077/ Abstract:This book seeks to challenge the classical yet still-dominant paradigm of international law, where ‘states’, as unitary and monolithic entities, are treated as the sole subjects of legal observation and regulation. It aims to offer a new paradigm for understanding and guiding recent human rights law practices, where both actors and norms are pluralised beyond a unitary and monolithic ‘state’ and international law as norms of, by and for ‘states’. It argues that each type of state organ – national courts, parliaments, administrative organs and national human rights institutions – bears different ‘duties’, independently from the obligations owed by the ‘state’ as a whole, and interacts with regional human rights courts and United Nations human rights treaty bodies in a principled manner under the ‘separation of powers in a globalised democratic society’ model. In this model, the ‘duties’ of state organs and their autonomous status in human rights treaties are anchored in the cooperative interactions between ‘inter-state organ norms’ on human rights and human rights treaties under global legal pluralism. This book uses the model to analyse and evaluate the current practices of human rights treaty organs and propose reforms where necessary. 大久保邦彦 （著書） 佐久間毅 編『新注釈民法(3)総則(3)』（有斐閣、2026年2月）https://www.yuhikaku.co.jp/books/detail/9784641017665 概要：時効障害の部分（580-689頁）の注釈を担当。時効についての本格的な注釈書は、『新版注釈民法』シリーズでは時効の部分が未完となったため、1967年刊行の『注釈民法(5)』以来、59年ぶりのものである。2017年の民法改正時も、時効障害に関する判例の全体像は十分に明確にされないまま、改正が行われた。本注釈ではまず、2017年時点の判例の全体像を明らかにした上で、時効障害制度を、時効の中断・停止から時効の更新・完成猶予へと再構成した改正法によって、何がどのように変わったのか、従前の判例はどこまで維持されるのかについて、できる限り客観的に記述した。理論的にも実務的にも重要な基本文献になったと自身では考えている。 川窪悦章 （その他の記事） 「企業の取引関係、マネジメント・プラクティス」RIETI Special Report, 2026年2月16日https://www.rieti.go.jp/jp/special/special_report/245.html 概要：企業成長の要因としては、企業内部の要因と外部の要因がある。企業内部の要因としては、R&D、イノベーション、デジタル・テクノロジー、あるいはマネジメント・プラクティスが挙げられる。企業外部の要因としては、インフラや金融制約、あるいは企業間の取引関係などがあり、取引関係を通じてショックが伝播される負のスピルオーバーや取引開始による成長機会という正のスピルオーバーが存在している。本稿では特に、企業の内部要因としてのマネジメント・プラクティスと、外部要因としての取引関係に焦点を当て、企業成長をどのように促進できるかについて議論する。 Takafumi Kawakubo （Discussion Paper） Makoto Hasegawa, Takafumi Kawakubo, Takafumi Suzuki, Masayoshi Hayashi“Tax-Motivated Transfer Pricing and Country-by-Country Reporting: Evidence from Japanese Customs Data”CIRJE Discussion Papers CIRJE-F-1266, January 2026https://www.cirje.e.u-tokyo.ac.jp/research/dp/2026/2026cf1266ab.html Abstract: Using Japanese firm-level customs data from 2014 to 2019, we investigate profit shifting through transfer pricing by Japanese multinational corporations. We find that Japanese firms reduce related-party export prices relative to arm’s-length prices as the tax differentials between Japan and destination countries widen, indicating tax motivated transfer pricing. The responsiveness of related-party prices to these tax differentials is, on average, smaller than that reported in previous studies but varies depending on transaction characteristics. Specifically, transfer mispricing is more pro nounced in transactions involving larger parent-affiliate pairs and products that are exported less frequently. We also examine the impact of the country-by-country re porting (CbCR) system, introduced in Japan in 2016, and find no evidence that it reduced transfer mispricing by Japanese multinationals subject to CbCR.