July 2026 – As part of the United States Supreme Court’s landmark June 30 decision upholding birthright citizenship, both Chief Justice John Roberts’ majority opinion and the concurring opinion authored by Justice Ketanji Brown Jackson relied extensively on historical sources and analysis provided to the Court in the amicus curiae brief filed by KBK Partner Richard B. Kendall on behalf of historians Martha S. Jones and Kate Masur.

In its 6–3 ruling, the Court reaffirmed the principle that children born in the U.S. are citizens and struck down a Trump administration executive order that sought to curtail birthright citizenship as outlined by the 14th Amendment of the U.S. Constitution.

KBK served as counsel of record for Martha Jones, a Professor of History at Johns Hopkins University, and Kate Masur, a Professor of History at Northwestern University, with whom it co-authored the brief in support of respondents in Trump v. Barbara. The brief demonstrated, based on Jones’ and Masur’s exhaustive research into the antebellum history preceding the adoption of the Fourteenth Amendment, that “the birthright principle constitutionalized in 1868 aimed to make a nation in which every person born in the United States is a citizen of the United States, no matter their status, color, heritage, means of entry, or immigration status of their parents.”

Jones and Masur showed that the Framers of the Fourteenth Amendment intended, in addition to granting citizenship to formerly enslaved people, to address decades of injustice inflicted through Black Laws, Black Codes, and the infamous Dred Scott decision upon free Black Americans born in the United States.

Both Chief Justice Roberts and Justice Jackson made extensive use of  the brief’s historical research and analysis. That history proves conclusively that the Trump Administration’s argument that the Fourteenth Amendment was intended only to confer citizenship on freed slaves is false. Justice Jackson cited nine pages of the historians’ brief in support of her opinion that Justice Thomas’ dissent was based on a flawed understanding of history, and her view that the Framers of the Fourteenth Amendment intended to and did enshrine universal birthright citizenship in our Constitution.

To read the amicus curiae brief in full, please click here.