In new book, liberal justice Stephen G. Breyer says conservative criticism of foreign references is “beside the point.” (Elise Amendola/AP)

The Supreme Court cannot do its job without a careful understanding of foreign law and practice, Justice Stephen G. Breyer argues in a new book, and conservative alarm about their use fails to reflect the new reality the justices face.

The court has become divided between those justices who consider foreign law as just another source in deciding tough cases and others who say that citing it is an improper and dangerous way to interpret American law and the Constitution. Some members of Congress and state legislatures have condemned this practice.

To Breyer, “Critics’ concerns about judicial references to foreign law are beside the point,” he writes in “The Court and the World: American Law and the New Global Realities,” which will be released this week.

“Their fears don’t much resonate when one understands the way in which foreign law and practices are actually considered,” he writes. “. . . It is not the cosmopolitanism of some jurists that seeks this kind of engagement but the nature of the world itself that demands it.”

It is the liberal Breyer’s third book trying to explain his view of how Supreme Court justices should decide cases and a gloved rebuke of conservative colleagues who disagree with him. He has already begun a round of media interviews that will include a visit with “Late Show” host Stephen Colbert.

In a telephone interview with The Washington Post, Breyer said the book was not just another episode in a long-running debate with his frequent sparring partner, Justice Antonin Scalia.

“I think of it as a report from the front,” where cases with international implications — national security, privacy, the environment, copyright, trade, treaties — make up an increasing part of the judicial docket, Breyer said.

“I would say 15 to 20 percent of the cases require the judges to know something about what happens abroad,” he said. “Sometimes facts, sometimes law, sometimes decisions.” At the same time, there is an ongoing “political argument that people say the court shouldn’t refer to or cite cases from foreign courts.”

“So when I compare that to what I actually see, I think something important is happening, and I think those who are talking about not citing foreign case law are basically barking up the wrong tree,” he said.

The controversy over judicial reference to foreign law is intense, Breyer wrote, but also relatively new. “Supreme Court justices from John Marshall to Felix Frankfurter have filed opinions with reference to decisions by foreign courts,” he wrote.

But Breyer said the first criticism of the practice he could find in a Supreme Court opinion came in 1988, when Scalia dissented from a decision that it was unconstitutional to impose the death penalty on someone who was younger than 16 at the time of the crime. (The court has since raised the minimum age to 18.)

Justice John Paul Stevens wrote in his opinion in that case that Western European nations and the Soviet Union would not impose such a penalty, a reference Scalia found “totally inappropriate.”

“We must never forget that it is a Constitution for the United States of America that we are expounding,” Scalia wrote. He added: “Where there is not first a settled consensus among our own people, the views of other nations, however enlightened the justices of this court may think them to be, cannot be imposed upon Americans through the Constitution.”

Since then, it has been Justice Anthony M. Kennedy who has drawn ire. In finding that the Constitution forbids state laws that criminalize homosexual sodomy, Kennedy cited similar decisions by foreign legislatures and courts. Breyer notes the court was overturning a previous court decision that said “Western civilization” had always condemned homosexuality.

Similarly, Kennedy wrote, in declaring that the Constitution’s prohibition of “cruel and unusual punishment” forbids the execution of intellectually disabled defendants, that the United States was virtually alone in allowing the practice.

To some on the court — most prominently Kennedy, Breyer and Justice Ruth Bader Ginsburg — examining such information from abroad is no different than reviewing the many studies or friend-of-the-court briefs that seek to influence their deliberations.

Decisions of foreign courts are not precedents, Ginsburg has said. But “why shouldn’t we look to the wisdom of a judge from abroad with at least as much ease as we would read a law review article from a professor?”

The court’s conservatives — Chief Justice John G. Roberts Jr. and Justices Scalia, Clarence Thomas and Samuel A. Alito Jr. — disagree. Foreign decisions can be relevant in some of the court’s cases that deal specifically with international issues but never in interpreting the Constitution, they say.

As Roberts noted in his confirmation hearing: “Domestic precedent can confine and shape the discretion of the judges. Foreign law, you can find anything you want. If you don’t find it in the decisions of France or Italy, it’s in the decisions of Somalia or Japan or Indonesia or wherever. As somebody said in another context, looking at foreign law for support is like looking out over a crowd and picking out your friends.”

Scalia was more succinct in a speech last year: “Who cares? We have our laws, they have theirs.”

Breyer and Scalia are the current court’s most prolific authors; Scalia has advised lawyers on how to make their case and his view of how to interpret legal texts. Breyer’s most recent book before the current effort was largely seen as a rebuttal to Scalia’s view that the correct way to interpret the Constitution is through the original meaning of the Founders’ words.

Thomas and Justice Sonia Sotomayor published popular autobiographies detailing their rise from poverty to the nation’s highest court, but the other justices have not expressed much interest in publishing. Justice Elena Kagan said recently that she didn’t think her background — the daughter of a lawyer and schoolteacher raised in Manhattan — would make a compelling read.

But Breyer’s choice of topic is not surprising. “He’s really the court’s internationalist,” said Eugene Volokh, a law professor at UCLA who recently published a law review article on the topic of foreign law and American courts.

Breyer does travel frequently abroad, speaks fluent French and is part of a small line of Americans, dating to Thomas Jefferson, admitted to the country’s Académie des Sciences Morales et Politiques.

Breyer, who turned 77 last month and is beginning the 22nd year of his lifetime appointment to the court, acknowledges that his approach has provoked concerns and presents his discussion in a kind of “let’s see what we can agree upon” style.

“I tend to have that kind of attitude, more than some,” Breyer said in the interview. “Work it out.”

That style, perhaps, is paying off. When Breyer’s last book came out five years ago, the reviews and interviews talked about the dissents he was writing in response to the court’s emerging conservative majority.

But in the term that ended in June, Breyer was in the majority more than any other justice. Has something changed, he is asked, or was it simply the composition of the term’s docket?

“Don’t know. The truthful answer is I don’t know,” he said. “Would I prefer to be in the majority? Yeah. Would I prefer that people agree with me all the time? Of course. So would you. So would anyone.”