Stephen guest writes mostly on legal and political philosophy, particularly concerning the question of justification in legal reasoning and the relationship between justice, interpretation and laws. His well-known book Ronald Dworkin appeared in its third edition in 2012 and was reviewed by Tom Nagel in the New York Review of Books. Amongst other work, he has published in Public Law on the role of the judiciary in revolutionary situations, the Law Quarterly Review on the logic of the law on hearsay evidence, the Journal of Medical Ethics on the moral and legal rights of the subjects of medical research, Acta Juridica on both the ideas of de facto and de jure legislatures in Southern Rhodesia, in Pakistan, in Nigeria and Ghana, and on the role of moral equality within legal reasoning, and Revue Internationale de Philosophie on the idea that law is a form of justice, to which Dworkin has published a reply.

In August 1998 he gave his father's 30th anniversary lecture - the F.W. Guest Lecture - at the University of Otago entitled 'Freedom and Status Revisited: Where Equality Fits In', which is published in the Otago Law Review 1999. His inaugural lecture, 'Why the Law is Just', was reviewed by Paul Johnson in The Spectator shortly afterwards, and is published in Current Legal Problems 2000. Johnson's main argument that treating people as equals makes no moral sense is at odds with his acceptance, presumably, as a prominent Roman Catholic, that all people are equal in the eyes of God.

In 2002, he was on the BBC's Radio 4 programme Unreliable Evidence, chaired by Clive Anderson, with Lord Bingham, Lord Carnworth and Professor John Gardner of the University of Oxford on the topic of the question whether there are legally right answers in appeal cases. He was alone in expressing the view that there were such answers, on the ground that disagreement would make no sense if it turned solely on questions of taste, although Lord Bingham later described this view as 'bizarre'. In 2009 he gave a public lecture at UCL entitled 'The Right to Obscene Thoughts' which was attended by many sex workers (several hundred), resulting in his being nominated as Academic of the Year by the Erotic Awards Committee of the Leydig Trust. He believes that hate speech should not be criminalised and in 2021 submitted a critical commentary to the New Zealand government on its proposals for "beefing up" hate speech crimes in the wake of the Christchurch massacre entitled 'Why Hate Should not be Part of the Criminal law'. 

In the past decade he has published essays on the legality of the Pitcairn child abuse prosecutions both for Oxford U.P. and the New Zealand Law Journal, on his father's experience as a POW lecturing on the University of London International degree programme in Stalag IVB in Muhlberg, Germany, and Campo 52 in Chiavari, Italy, on misinterpretation of Dworkin in Shapiro's Legality in Analysis Reviews, on Dworkin's Justice for Hedgehogs in Ethics and International Affairs, on the morality of the unity of law thesis in the Ukraine Law Review and on the Humean principle in law and morality in the Mexican journal Problema. He has recently written a Personal Note on Ronald Dworkin.