The 2021 Supplement incorporates important developments that have arisen or deepened since the publication of the sixth edition of the casebook in 2020. These developments include Notes on Reconciliation and the Filibuster in Chapter 1; Supreme Court decisions addressed to the law of representational structures in Chapter 2 (Brnovich v. Democratic National Committee) and to theories of statutory interpretation in Chapter 5 (Bostock v. Clayton County and Niz-Chavez v. Garland); extended Notes on original public meaning and a newer textualism in Chapter 5 and a Note on continuing debate over the series qualifier canon in Chapter 6 (Facebook Inc. v. Duguid).

The Supplement further includes treatment of a number of recent Supreme Court decisions in Chapter 8, on appointment and removal (Seila Law LLC v. Consumer Finance Protection Bureau; Collins v. Yellin; and United States v. Arthrex); on notice and comment rulemaking (Federal Communications Commission v. Prometheus Radio Project); and on judicial review of agency rules (Department of Homeland Security v. Regents of the Univ. of California); and an extended Note on Executive Orders and the Regulatory Process in the Trump and Biden Eras. Finally, the Supplement covers a recent Supreme Court decision addressing deference to agency interpretations in Chapter 9 (Epic Systems Corp. v. Lewis).