Book VI of the Vox Clamantis is Gower's most important analysis of England's legal system. Except for its remarks about the king, however, the book is hardly noted in the context of medieval legal studies or even in work on Gower. It is substantial, comprising 1366 lines divided into twenty-one chapters, slightly less than half of which are devoted to an open letter to Richard II (Chapters 8–18) that is its climax. This speculum principis is the energy-absorbing black hole of Book VI, indeed of the entire Vox Clamantis after the conclusion of the Visio Anglie. Addressed to young Richard in his capacity as head of state and law, it has attracted such attention, ever since G. C. Macaulay indicated how Gower's thought about the king evolved, that the poet's focus on the law's other representatives has gone largely unnoticed. Maria Wickert devoted an entire chapter to this Fürstenspiegel in her groundbreaking Studien zu John Gower, and John Fisher, whose views on the Vox were shaped throughout his own study by Wickert's conclusions, considered it the midpoint in the poet's evolving thought about his young monarch: “In its final form […] the Vox Clamantis and Cronica Tripertita […] become a unified commentary on the tragic course of Richard's rule from 1381 to 1400, with a prologue (the Visio), a midpoint (the Epistle), and an epilogue (the Cronica).” The speculum principis occupies centerstage in an evolving royal drama, and the A- and B-Text variants at its beginning and conclusion bracket the tipping point in Gower's changing opinions about the monarch he once thought to guide.

Book VI also contains a considerable amount of commentary on other aspects of the legal system. Most important for our purposes is Chapter 5, an open letter to the judiciary who preside over England's common-law courts. This chapter comprises the first instance of an epistle in the sixth book, and it has gone largely unnoticed and unremarked. Wickert notes its existence dismissively at the outset of her detailed discussion of the open letter to the king and passes it over without investigation. Yet it comprises an entire chapter of Book VI and is introduced, like the letter to the king, by an anticipatory chapter. It is therefore a substantial component of Gower's survey of the law.