Les Green is the Professor of the Philosophy of Law and Fellow of Balliol College.  He also holds an appointment as Professor of Law and Distinguished University Fellow at Queen's University in Canada.  After beginning his teaching career as a fellow of Lincoln College, Oxford, he moved to Osgoode Hall Law School in Toronto.  He has also been a visiting professor at many other law faculties, including Berkeley, NYU, Chicago and, for some years, at the University of Texas at Austin.  Professor Green writes and teaches in the areas of jurisprudence, constitutional theory, and moral and political philosophy.  He serves on the board of several journals and is co-editor of the annual Oxford Studies in Philosophy of Law and of the book series Oxford Legal Philosophy.

Professor Green is in Canada on sabbatical leave in 2019-2020.


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  • Leslie Green, 'Gender and the Analytical Jurisprudential Mind' (2020) Modern Law Review 893
    This paper replaces the SSRN draft of the same title.
    Because gender norms shape the content and application of the law, feminist scholarship has a lot to contribute to the study of law. Gender is also relevant to several problems in normative jurisprudence, and to some problems in special jurisprudence (the study of concepts in the law). But gender has no relevance to general jurisprudence, for there is no sense in which the concept of law is ‘gendered’, and no answer to leading problems in general jurisprudence depends on any thesis about gender. Yet some scholars, including Joanne Conaghan, argue that gender is pervasively relevant to jurisprudence. She says its relevance has been screened out by three errors that characterize what she calls ‘the analytical jurisprudential mind’: a belief that legal concepts are unchanging, that description is value-neutral, and that empirical evidence is irrelevant to jurisprudence. I show that none of these charges can be sustained. By way of example, I show how analytical methods handle the relationship between sex and gender and the place of sex in the law of marriage. Hostility to analytical methods is likely to be damaging to feminist legal theory, and I urge feminist scholars in law to consider the now-plentiful resources in analytic legal philosophy that treat the topics of interest to them.
  • Leslie Green, 'Positivism, Realism, and Sources of Law' in S. Mendus and T. Spaak (eds), Cambridge Companion to Legal Positivism (Cambridge University Press 2019) (forthcoming)
    The SSRN version is the author's penultimate manuscript of the accepted version.
    This paper explores the relationships between legal positivism and legal realism. Legal positivists hold that all law is positive law, that it is based on social sources. The law is therefore incomplete: there are legal disputes that cannot be determined by law alone. But legal realists seem to presuppose that all law is positive, and they affirm that, at least in appellate cases, judicial decisions are underdetermined by positive law. Are realists therefore legal positivists? In temper and outlook the doctrines are similar. My argument is that, after some conceptual errors are set aside, one difference lies in their respective attitudes to sources of law. Positivists hold that many sources of law are binding, at least on judges. Legal realists hold that many sources are permissive only: even domestic statutes and cases often have little more authority than, e.g. a doctrine of foreign law. That, in addition to the more familiar sources of indeterminacy acknowledged by positivists and realists alike, helps explain why realists think law is so loosely controlling in court, and why it is often defeated by considerations of policy and preference.
  • Leslie Green, 'Escapable Law' (2019) 19 Jerusalem Review of Legal Studies 110
    Morality judges law, but law does not judge morality. It counts against a law that it is immoral, but it does not count against a sound moral principle that it is illegal. John Gardner offers an intriguing explanation of this fact. He claims that we can always demand a non-legal reason for acting in accordance with the law, but that it makes no sense to ask for a non-moral reason for acting in accordance with morality: morality is 'inescapable'. I explore, but ultimately reject, this explanation. I have doubts about Gardner's account of the normativity of law, and about his notion of what it is for a norm to be 'inescapable'. I also have doubts about his view, shared by many natural lawyers that, in its paradigm case, law is morally obligatory. The asymmetry between the normative authority of law and morality is a feature of their (claimed) respective jurisdictions.
    ISBN: ISSN 2219-7117
  • Leslie Green, 'Der Positivismus und die Untrennbarkeit von Recht und Moral' in Felix Koch, Amir Mohseni and David P. Schweikard (eds), Analytische Rechtsphilosophie: Grundlagentexte (Suhrkamp Verlag 2019)
    Translated by Lisa Müller and Felix Koch. First published as ‘Positivism and the Inseparability of Law and Morals,’ 83 New York University Law Review (2008), 1035-1058.
    ISBN: 978-3-518-29819-0
  • Brian Leiter, Leslie Green and John Gardner (eds), Oxford Studies in Philosophy of Law, Vol III (3 Oxford University Press 2018)
  • Leslie Green, 'Law and the Role of a Judge' in K.K. Ferzan and S.J. Morse (eds), Legal, Moral, and Metaphysical Truths (Oxford University Press 2016)
    This paper argues that role of a judge consists of obligations to apply the law, obligations to improve the law, and obligations to protect the law. It defends this view against a competing suggestion by Michael Moore, who claims that, when acting judicially, judges are always obligated to apply the law, and the law alone. I argue that this depends on an incorrect view of the relationship between social roles and moral obligations, and an unacceptably capacious view of what the law is. I conclude by asking whether there nonetheless room to make a conceptual choice to see law in the way I reject, or a reason to reform the concept of law along those lines. I reject both ideas. There are fewer conceptual choices in jurisprudence than some people think.
    ISBN: 978-0-19-870324-2
  • Leslie Green, 'Pornographies' in Nicholas Bamforth (ed), Sexual Orientation and Human Rights (Ashgate, International Library of Essays on Rights 2014)
    Reprinting 'Pornographies', first published 8 Journal of Political Philosophy, (2000), 27-52.
    ISBN: 978-1-4094-3040-7
  • Leslie Green, 'Reconsiderando El Concepto de Derecho' in S F Rubio (ed), Hart en la Teoria del Derecho Contemporanea (Ediciones Universidad Diego Portales 2014)
    Spanish translation by Erensto Riffo of 'The Concept of Law Revisted', first published in 94 Michigan Law Review 1687 (1996)
  • Leslie Green, 'Should Law Improve Morality?' (2013) 7 Criminal Law and Philosophy 473
    DOI: 10.1007/s11572-013-9248-3
    Lawyers and philosophers have long debated whether law should enforce social morality. This paper explores whether law should improve social morality. It explains how this might be possible, and what sort of obstacles, factual and moral, there are to doing so. It concludes with an example: our law should attempt to improve our social morality of sexual conduct.
    ISBN: 1871-9791
  • L Duarte d'Almeida, J Gardner and Leslie Green (eds), Kelsen Revisited: New Essays on the Pure Theory of Law (Hart Publishing 2013)
    Forty years after his death, Hans Kelsen (1881-1973) remains one of the most discussed and influential legal philosophers of our time. This collection of new essays takes Kelsen's Pure Theory of Law as a stimulus, aiming to move forward the debate on several central issues in contemporary jurisprudence. The essays in Part I address legal validity, the normativity of law, and Kelsen's famous but puzzling idea of a legal system's 'basic norm'. Part II engages with the difficult issues raised by the social realities of law and the actual practices of legal officials. Part III focuses on conceptual features of legal systems and the logical structure of legal norms. All the essays were written for this volume by internationally renowned scholars from seven countries. Also included, in English translation, is an important polemical essay by Kelsen himself.
    ISBN: 9781849464567
  • Leslie Green and Brian Leiter (eds), Oxford Studies in Philosophy of Law vol II (Oxford University Press 2013)
    ISBN: 9780199679829
  • Leslie Green, 'Sex-Neutral Marriage' in J Feinberg, J Coleman, and C Kutz (eds), Philosophy of Law (Cengage Learning 2013)
  • Leslie Green, The Authority of the State (Chinese Edition) (China University of Political Science and Law Press 2013)
    ISBN: 7562046468
  • Leslie Green, 'The Morality in Law' in L Duarte d'Almeida, J Edwards, and A Dolcetti (eds), Reading H.L.A. Hart's The Concept of Law (Hart Publishing 2013)
  • Leslie Green, 'Introduction to the Concept of Law' in (ed), The Concept of Law, 3rd Edition (Oxford University Press 2012)
  • Leslie Green, 'Jurisprudence for Foxes' (2012) 3 Transnational Legal Theory 150
    DOI: 10.5235/TLT.3.2.150
    This paper contests Brian Simpson's claim that HLA Hart's book, The Concept of Law, is that of a 'hedgehog,' that is, a procrustean and monistic thinker. It is not. Hart's work is pluralist both in its explanatory concepts and in its evaluative background. It is, of course, a philosophical book; but that is not enough to make it monistic. Some conjectures are offered as to why Simpson so badly misunderstood Hart, and as to why analytic legal philosophy is misunderstood, or distrusted, more generally.
  • Leslie Green, 'Obscenity without Borders' in F Tanguay-Renaud and J Stribopolous (eds), Rethinking Criminal Law Theory (2012)
    ISBN: 9781849460101
  • Leslie Green, 'The Nature of Limited Government ' in R George and J Keown (eds), Reason, Morality, and the Law: The Jurisprudence of John Finnis (Oxford Univiersity Press 2012)
  • Leslie Green, 'What is Freedom For?' (2012) Oxford Legal Studies Research Paper
    Two conceptions of the value of political freedom are popular. According to one, freedom serves autonomy, creating one’s own path through life. According to the other, freedom serves authenticity, keeping faith with an identity one did not choose. This paper bridges the gap between these views in several ways. It shows that autonomy embraces some of the unchosen aspects of life that authenticity stresses, and that authenticity is consistent with scope for choice within an unchosen identity. It is also shows that both views share a stake in a neglected value, self-knowledge. Partisans of authenticity cannot keep faith with their identity if they do not know what it truly is. Partisans of autonomy cannot choose a path in life without knowing what the options are for them, and these options can be affected instrumentally and constitutively by their identity, which they therefore have a stake in knowing. Of course, there can be more than one sound argument in favor of freedom. But contrary to what many suppose, autonomy and authenticity are complementary, not competing, in making that case. The differences between them are matters of nuance and degree.
  • Leslie Green, 'Sex-Neutral Marriage' (2011) 64 Current Legal Problems 1
    DOI: 10.1093/clp/cur014
    A different-sex marriage need not be a marriage between heterosexuals, and a same-sex marriage need not be a marriage between homosexuals. This shows how little the law of marriage cares about the sexuality of parties to a marriage; it does not show that sex-restricted marriage laws do not discriminate on grounds of sexual orientation. They do. Neither does the law care much about sex, let alone possibly procreative sex, within marriage. The voidability of a different-sex marriage on grounds of non-consummation does not show otherwise. The formation of a valid marriage was always a matter of consent, not coitus. But what should happen to the doctrine of non-consummation in a sex-neutral marriage regime? It is an anachronism that should be abolished.
    ISBN: 0070-1998
  • Leslie Green and Brian Leiter (eds), Oxford Studies in Philosophy of Law Vol I (Oxford University Press 2011)
    ISBN: 978-0-19-960533-3
  • Leslie Green, 'El Positivismo y la inseparabilidad del derecho y la moral' in M.E. Orellana Benada (ed), Causas Perdidas: ensayos de filosofia juridica, politica y moral (Catalonia 2010)
  • Leslie Green, 'General Jurisprudence' in Michael Giudice, Wil Waluchow, and Maksymilian del Mar (eds), The Methodology of Legal Theory, vol. I (Ashgate 2010)
  • Leslie Green, 'Law as a Means' in P Cane (ed), The Hart-Fuller Debate in the Twenty-First Century (Hart Publishing, Oxford 2010)
    ISBN: 978-1-84113-894-7
  • Leslie Green, 'The Germ of Justice' (2010) Oxford Legal Research Papers
    This paper addresses the perennial question of the relationship between law and justice. HLA Hart argued that ‘we have, in the bare notion of applying a general rule of law, the germ, at least, of justice.’ If true, this establishes a necessary connection between law and morality. That is no objection, for the so-called ‘separability thesis’ is anyway false. But the ‘germ-of-justice’ thesis is also false. Justice is a matter of the correct allocation of benefits and burdens among people. Contrary to what Hart and others think, there is not necessarily any injustice in failing to apply a valid legal rule, not even an ‘administrative’ injustice. It is readily conceded that ‘formal justice’ is not enough in law, that we also need ‘substantive justice’. This too is a mistake. Formal justice is not insufficient; it is incoherent--all justice is substantive. Might constant rule-application do justice by promoting impartiality? Not necessarily. It depends on the content of the rules and on the nature of the of the adjudicator’s prejudices. There is nonetheless a weak connection between law and justice. Every legal system has courts whose job it is to aim at justice: they must decide not only whether plaintiff deserves a remedy, or whether the prosecution is entitled to a conviction, but also whether these should be ordered in the face of a claim to the contrary. Courts have an allocative job to do. This does not show that they must achieve justice, or even a minimum of justice. Nor does it show that justice is the first virtue of legal institutions. The connection between law and justice is real, but modest. Justice is a necessary aim of a necessary legal institution.
  • Leslie Green, 'Filosofia del derecho general' (2009) 3 Problema: anuario de filosofia y teoria del derecho 289
    Spanish translation of 'General Jurisprudence: a 25th Anniversary Essay'. Translated by Enrique Rodriguez Trujano & Pedro A. Villarreal Lizarraga.
  • Leslie Green, 'Positivism and the Inseparability of Law and Morals' (2008) 83 New York University Law Review 1035
    This article seeks to clarify and assess HLA Hart's famous claim that legal positivism somehow involves a “separation of law and morals.” The paper contends that Hart's “separability thesis” should not be confused with the “social thesis,” with the “sources thesis,” or with a methodological thesis about jurisprudence. In contrast to all of these, Hart's separability thesis denies the existence of any necessary (conceptual) connections between law and morality. But that thesis is false: there are many necessary connections between law and morality, some of them conceptually significant. Among them is an important negative connection: law is of its nature morally fallible and morally risky. Lon Fuller emphasized what he called the “internal morality of law,” the “morality that makes law possible”. Hart’s most important message is that there is also an immorality that law makes possible. Law's nature is seen not only in its internal virtues, in legality, but also in its internal vices, in legalism.
    ISBN: 0028-7881
  • Leslie Green, 'On Being Tolerated' in M Kramer, C Grant, B Colborn, A Hatzistavrou (ed), The Legacy of HLA Hart: Legal, Political, and Moral Philosophy (Oxford University Press 2008)
    Why is it that toleration can be uncomfortable for the tolerated? And how should tolerators respond to that discomfort? This paper argues that properly directed toleration can be deficient in its scope, grounds or spirit. That explains some of the discomfort in being tolerated. Beyond this, the occasions for toleration¿the existence of a power to prevent and of an adverse judgment¿can also make toleration sting. The paper then explores and rejects two familiar suggestions about how one should respond to this discomfort: with acceptance or recognition of the tolerated. It is proposed instead that toleration should be supplemented by understanding. The nature and importance of this attitude are assessed.
    ISBN: 978-0-19-954289-5
  • Leslie Green, 'Sexuality, Authenticity and Modernity' in J Feinberg & J Coleman (ed), Philosophy of Law, 8th Edition (Cengage Publishing 2007)
    ISBN: 9780495095057
  • Leslie Green, 'Who Believes in Political Obligation?' in Shinggui Mao trans (ed), Political Obligation: Justifying and Refuting (Nanjing: Jiangsu People's Publishing House 2007)
  • Leslie Green, 'The Duty to Govern' (2007) 13 Legal Theory 165
    DOI: 10.1017/S1352325208070079
  • Leslie Green, 'Men in the Place of Women, from Butler to Little Sisters' (2006) 44 Osgoode Hall Law Journal 1
    ISBN: 0030-6185
  • Leslie Green, 'Three Themes from Raz' (2005) 25 Oxford Journal of Legal Studies 503
    ISBN: 0143-6503
  • Leslie Green, 'Associative Obligations and the State' in Justine Burley (ed), Dworkin and his Critics (Blackwell 2004)
    ISBN: 631197656
  • Leslie Green, 'Civil Disobedience and Academic Freedom' (2003) 41 Osgoode Hall Law Journal 380
  • Leslie Green, 'Legal Obligation and Authority' (2003) Stanford Encyclopedia of Philosophy
    Whatever else they do, all legal systems recognize, create, vary and enforce obligations. This is no accident: obligations are central to the social role of law and explaining them is necessary to an understanding of law's authority and, therefore, its nature. Not only are there obligations in the law, there are also obligations to the law. Historically, most philosophers agreed that these include a moral obligation to obey, or what is usually called “political obligation.” Voluntarists maintained that this requires something like a voluntary subjection to law's rule, for example, through consent. Non-voluntarists denied this, insisting that the value of a just and effective legal system is itself sufficient to validate law's claims. Both lines of argument have recently come under intense scrutiny, and some philosophers now deny that law is entitled to all the authority it claims for itself, even when the legal system is legitimate and reasonably just. On this view there are legal obligations that some of law's subjects have no moral obligation to perform.
  • Leslie Green, 'Legal Positivism' (2003) Stanford Encyclopedia of Philosophy
    Legal positivism is the thesis that the existence and content of law depends on social facts and not on its merits. The English jurist John Austin (1790-1859) formulated it thus: “The existence of law is one thing; its merit and demerit another. Whether it be or be not is one enquiry; whether it be or be not conformable to an assumed standard, is a different enquiry.” (1832, p. 157) The positivist thesis does not say that law's merits are unintelligible, unimportant, or peripheral to the philosophy of law. It says that they do not determine whether laws or legal systems exist. Whether a society has a legal system depends on the presence of certain structures of governance, not on the extent to which it satisfies ideals of justice, democracy, or the rule of law. What laws are in force in that system depends on what social standards its officials recognize as authoritative; for example, legislative enactments, judicial decisions, or social customs. The fact that a policy would be just, wise, efficient, or prudent is never sufficient reason for thinking that it is actually the law, and the fact that it is unjust, unwise, inefficient or imprudent is never sufficient reason for doubting it. According to positivism, law is a matter of what has been posited (ordered, decided, practiced, tolerated, etc.); as we might say in a more modern idiom, positivism is the view that law is a social construction. Austin thought the thesis “simple and glaring.” While it is probably the dominant view among analytically inclined philosophers of law, it is also the subject of competing interpretations together with persistent criticisms and misunderstandings.
  • Leslie Green, 'Strategy and Fundamental Legal Rules' (2003) American Philosophical Association Newsletter on Law and Philosophy 69
  • Leslie Green, 'Law and Obligations' in J. Coleman and S. Shapiro (eds), The Oxford Handbook of Jurisprudence and Philosophy of Law (OUP 2002)
    ISBN: 0198298242
  • Leslie Green, 'Pluralism, Social Conflict, and Tolerance' in A Soeteman (ed), Pluralism and Law (Springer 2001)
    ISBN: 0792370392
  • Leslie Green, 'Pornographies' (2000) 8 Journal of Political Philosophy 27
  • Leslie Green, 'Same-Sex Marriage Consultation' (2000) British Academy
    A public debate on the government's consultation paper on same-sex marriage.
  • Leslie Green, 'Positivism and Conventionalism' (1999) 12 Canadian Journal of Law and Jurisprudence 35
  • Leslie Green, 'Sexuality, Authenticity, and Morality' in J Feniberg and J Coleman (eds), Philosophy of Law, 5th Ed. (Wadsworth 1999)
  • Leslie Green, 'Who Believes in Political Obligation?' in W Edmundson (ed), The Duty to Obey the Law (Rowman and Littlefield 1999)
  • Leslie Green, 'Authority' in E Craig (ed), Routledge Encyclopedia of Philosophy (Routledge 1998)
  • Leslie Green, 'Pornographizing, Subordinating, and Silencing' in R Post (ed), Censorship and Silencing: Practices of Cultural Regulation (Getty Research Institute 1998)
  • Leslie Green, 'Power' in E Craig (ed), Routledge Encyclopedia of Philosophy (Routledge 1998)
  • Leslie Green, 'Rights of Exit' (1998) 4 Legal Theory 165
  • Leslie Green, 'The Functions of Law' (1998) 12 Cogito 117
  • Leslie Green, 'Freedom of Expression and Choice of Language' in E Soifer (ed), Ethical Issues: Perspectives for Canadians (Broadview Press 1997)
  • Leslie Green, 'The Concept of Law Revisited' (1997) 94 Michigan Law Review 1687
  • Leslie Green, 'Who Believes in Political Obligation?' in J Narveson & JT Sanders (ed), For and Against the State (Rowman and Littlefied 1996)
  • Leslie Green, 'Internal Minorities and their Rights' in W Kymlicka (ed), Rights of Cultural Minorities (Oxford University Press 1995)
  • Leslie Green, 'Freedom of Expression and Choice of Language' in WJ Waluchow (ed), Free Expression: Essays in Law and Philosophy (Oxford University Press 1994)
  • Leslie Green, 'Internal Minorities and their Rights' in J Baker (ed), Group Rights (University of Toronto Press 1994)
  • Leslie Green, 'Les minorites internes et leurs droits' (1994) 4 Lekton 81
  • Leslie Green, 'Concepts of Equity in Taxation' in A Maslove (ed), Fairness in Taxation: Exploring the Principles (University of Toronto Press 1993)
  • Leslie Green and Denise Reaume, 'Bilingualism, Territorialism, and Linguistic Justice' (1991) 1 Network: Newsletter on the Constitution
  • Leslie Green, 'Consent and Community' in J Raz (ed), Authority (Blackwell 1991)
  • Leslie Green, 'Freedom of Expression and Choice of Language' (1991) 13 Law and Policy 215
  • Leslie Green, 'Two Views of Collective Rights' (1991) Canadian Journal of Law and Jurisprudence 315
  • Leslie Green, 'Consent and Community' in P Harris (ed), On Political Obligation (Routledge 1990)
  • Leslie Green, 'Legal Ethics: Sociology and Morality' in D MacNiven (ed), Moral Expertise (1990)
  • Leslie Green and D Reaume, 'Second Class Rights? Principle and Compromise in the Charter' (1990) 13 Dalhousie Law Journal 564
  • Leslie Green, The Authority of the State (Clarendon Press 1990)
    ISBN: 978-0-19-827313-4
  • Leslie Green, 'Associative Obligations and the State' in L Green and A Hutchinson (eds), Law and the Community: The End of Invidualism? (Carswell 1989)
  • Leslie Green and D Reaume, 'Education and Linguistic Security in the Charter' (1989) 34 McGill Law Journal 777
  • Leslie Green and Allan C. Hutchinson (eds), Law and the Community: The End of Individualism? (Carswell 1989)
    ISBN: 978-045-933481-9
  • Leslie Green, 'Law, Legitimacy and Consent' (1989) Southern California Law Review 795
  • Leslie Green, 'Loyalty, Security, and Democracy' in P Hanks and JD McCamus (eds), National Security: Surveillance and Accountability in a Democratic Society (Yvon Blais 1989)
  • Leslie Green, 'Kant's Liberalism: A Reply to Rolf George' (1988) 27 Dialogue 207
  • Leslie Green, 'Un-American Liberalism: Raz's Morality of Freedom' (1988) 38 University of Toronto Law Journal 317
  • Leslie Green, 'Are Language Rights Fundamental?' (1987) 25 Osgoode Hall Law Journal 639
  • Leslie Green, 'The Political Content of Legal Theory' (1987) 17 Philosophy of the Social Sciences 1
  • Leslie Green, 'Law's Rule' (1986) 24 Osgoode Hall Law Journal 1023
  • Leslie Green, 'Authority and Convention' (1985) 35 Philosophical Quarterly 329
  • Leslie Green, 'Legality and Community' (1985) 5 Oxford Journal of Legal Studies
    ISBN: 463-470
  • Leslie Green, 'Support for the System' (1985) 15 British Journal of Political Science 127
  • Leslie Green, 'What is a Dictator?' (1985) 45 Analysis 125
  • Leslie Green, 'The Techniques and Limits of Law' (1984) 9 Queen's Law Journal 328
  • Leslie Green, 'Dictators and Democracies' (1983) 43 Analysis 58
  • Leslie Green, 'Law, Co-ordination and the Common Good' (1983) 3 Oxford Journal of Legal Studies 299

Research programmes

Research Interests

Legal Philosophy, Jurisprudence, Constitutional Theory, Human Rights

Options taught

Jurisprudence, Moral and Political Philosophy, Jurisprudence and Political Theory

Research projects