Reaching back into 17^th Century English history and relying anew on the burst of new civil rights after America’s Civil War, a deeply divided Supreme Court on Tuesday assured U.S. citizenship as a constitutional right of every child born in this country.

The decision frustrates an effort by President Trump to take away citizenship for any child whose parents are in the United States illegally or are here temporarily to work, study or tour.  The decision nullified that key part of a presidential order that Trump had issued on the first day of his new term in the White House.

The ruling is expected to protect the citizenship of about 200,000 children born each year to foreign-born parents living here, legally or not.

The outcome was not a surprise, but it was not supported as broadly as many legal observers had expected.  The final vote on the constitutional guarantee of citizenship was by the narrowest margin, 5-to-4.  Chief Justice John G. Roberts, Jr., a conservative, and his conservative colleague Justice Amy Coney Barrett, joined with the Court’s three liberal Justices in solidifying anew the Fourteenth Amendment’s birthright citizenship clause.   Those three were Ketanji Brown Jackson, Elena Kagan and Sonia Sotomayor.

The majority traced that right back to the common law of England as early as 1608, in a much-studied court ruling in what is called Calvin’s Case establishing the rights to English citizenship for those living in Scotland after the king of Scotland became England’s king, too.

The Chief Justice’s opinion also found sturdy support throughout U.S. history, with a strong reliance on what is often called America’s “Second Founding” – the creation of new rights during the Reconstruction era following the Civil War.  The birthright citizenship promise is in the opening clause of the Constitution’s Fourteenth Amendment.

The Court also reaffirmed its own 1898 precedent in the case of United States v. Wong Kim Ark, a decision that protected the citizenship of an American-born man whose parents were Chinese.  That decision came in an era of aggressive efforts by the United States government to exclude Chinese nationals, particularly laborers who had come to this country to build the railroads.

It had been expected, after the Court heard the new case in April, that the citizenship guarantee would have the support of at least six of the Justices.  However, one of the conservative Justices, Brett M. Kavanaugh, disagreed with the majority that citizenship at birth was a constitutional right.  He did conclude in an opinion speaking for himself that a 1952 federal law does protect a similar right.  By that view, of course, Congress could change its mind and cast aside that law.

Three of the Court’s conservative members, Justice Samuel A. Alito, Jr., Neil M. Gorsuch and Clarence Thomas, wrote separate dissenting opinions, each providing at least some support for Trump’s ban and each finding that the Fourteenth Amendment clause did not reach all children born in this country.

Alito expressed deep fears that the ruling would increase illegal immigration of parents seeking citizenship for any children born here.  Gorsuch, in the briefest of any of the opinions in the case (three pages), voiced some doubts about the issue but wound up concluding that the citizenship guarantee is only for those who have a permanent home in the United States.  Thomas went the furthest in disagreement, arguing that the citizenship clause was intended only to give that status to slaves who had won their freedom.

The ruling came in the case titled Trump v. Barbara.  The name Barbara was a pseudonym for a woman from Honduras, now living in New Hampshire.  She fled to the United States two years ago to be free from mob violence in her home country.  She joined with other parents and newborn children in challenging the Trump order.

The decision was the final one issued by the Court among those heard during the current term.  The Court will be on a summer recess until a new term begins on October 5.  Though in recess, it will continue to act on emergency issues.

On Tuesday, the Court issued two other significant rulings, both on 6-to-3 votes, split along the customary ideological lineups.

In a pair of cases decided together, the Court ruled that neither the Constitution’s guarantee of equality of the sexes nor a federal civil rights law gave transgender girls a right to participate in girls’ sports in public schools and colleagues.  The decision in the case of West Virginia v. B.P.J., apparently was limited to participation in sports, and thus did not set a broader precedent against transgender rights.

In a ruling that reinforced the conservative Court majority’s deep skepticism of laws that restrict the flow of money into election campaigns, the Court struck down ceilings on the amount of money that political parties can spend when they do so in coordination with their parties’ candidates.  That was the decision in National Republican Senatorial Committee v. Federal Election Commission, relying on the free-speech clause of the First Amendment.  (Under a series of rulings in the modern era, the Court has treated campaign spending as a form of speech on a theory that financing of campaigns is a form of political expression.)