How did this case arise?
Trump signed Executive Order 14160 the day after his second inauguration, directing federal agencies to stop recognizing citizenship for children born to undocumented parents or parents on temporary visas. The plaintiff who took it down used a pseudonym: Barbara fled the Mara 18 gang in Honduras with her husband and three children, settled in New Hampshire, and was pregnant when she learned Trump’s order claimed her unborn child wouldn’t be American.

A federal judge sided with her and the ACLU. The case climbed to the Supreme Court, which on the way there had already gutted nationwide injunctions in the related case Trump v. CASA — a procedural ruling that forced Barbara’s lawyers to refile as a class action just to keep the fight alive.

Decision Overview
The Supreme Court ruled Tuesday that children born in the United States to parents who are unlawfully or temporarily present in the U.S. remain citizens at birth. The chief justice didn’t hedge. Roberts wrote “Citizenship, then and now, was the right to have rights — to freely participate in our political community. The Framers of the Fourteenth Amendment extended that promise to ‘every free-born person in this land.’ We keep that promise today.”

In Trump v. Barbara (Birthright Citizenship) (25–365), the Court split 6–3, with Roberts joined by Justices Sonia Sotomayor, Elena Kagan, Amy Coney Barrett and Ketanji Brown Jackson finding the president’s executive order unconstitutional, while Justice Brett Kavanaugh wrote separately that the order violates federal law. Justices Clarence Thomas, Samuel Alito and Neil Gorsuch dissented.

This decision will protect the citizenship of about a quarter million babies born each year. However, the issue is not settled. House Speaker Mike Johnson has confirmed that House Republicans are examining legal strategies to get around the Court’s ruling.

Breakdown of Opinions and Analysis
How did each side form its majority or dissenting opinions? Both used much of the same source material, primarily the 1898 case of United States v. Wong Kim Ark (which has stood since 1898). Eight U.S.C. § 1401(a) codifies it, in which a person born in the United States to parents of Chinese descent was held to be a citizen, but each opinion assembled different legal worlds from it. The Roberts majority treated birth in the United States, coupled with subjection to U.S. sovereign authority, as enough to establish citizenship under the 14th Amendment.

Dissents, on the other hand, focused on a more demanding concept of allegiance, especially for children of temporary visitors and unlawfully present parents.

To better understand how each side shaped differing opinions from the same source material, It is helpful to examine the differences of each in length, vocabulary, precedent use, and conceptual structure as justification and rationale for their conclusions. The majority opinion is relatively compact in length, while the dissents supply most of the historical excavation and counter-history. Thomas’ dissent was more than three-and-a-half times the length of the Roberts majority.

In the vocabulary used by the Roberts majority, territorial/common-law terms (the nature of birthright citizenship at the founding) accounted for 29.5% of the conceptual structure in his opinion. In the dissents, the same accounted for only 9.3%. A larger share of their vocabulary referenced domicile (where one makes their permanent home), exclusive allegiance, immigration status, and tribal-citizenship exception analogies.

Revisionist History, Revisionist Precedent
The dissents also moved in the opposite direction on domicile and immigration-status language.

Allegiance is the notable counterexample. The Roberts majority used allegiance much more intensively than the dissents, supporting the point that the majority did not avoid allegiance; it defined it through birth, protection, and territorial jurisdiction rather than through parental domicile or exclusive national allegiance.

Both sides argued that US v. Kim Ark supported their positions. Kavanaugh’s separate opinion had the highest relative mention of this precedent (17 times) given the briefness of his opinion, in which he argued that Wong Kim Ark was not inconsistent with his view that birthright citizenship was not constitutionally guaranteed.

Further Analysis: 5-4 Podcast Episode, SCOTUS Blog, Aaron Reichlin-Melnick

(Taken from an email sent to me by Never Again Action. Emphasis original.)