In early 2016, Justice Antonin Scalia died suddenly of a heart attack on a Texas ranch, sending his Supreme Court colleagues into a period of grief and uncertainty. Behind closed doors, they had to contend with another piece of unsettling news. Justice Scalia, the leading light of the conservative legal movement, had left no plans for his working papers, according to five people aware of the situation.

For a Supreme Court justice, this was the equivalent of dying without a will. With no instructions for creating an archive or opening it to the public, the definitive inside account of his work — and the court’s — could be lost or emerge with uncomfortable speed. So following his death, his colleagues entered into private negotiations to try to head off any such situation in the future.

In a series of memos and conference meetings, Chief Justice John G. Roberts Jr. led the surviving justices in discussions about imposing a more uniform seal for their own papers, according to several people with knowledge of the process. The absence of instructions from Justice Scalia and ensuing confidential conversations, which have not previously been reported, help explain why the nation’s highest court can be so difficult to understand.

The ultimate record of the court’s work is considered the personal property of each justice, to dispose of or share as he or she chooses. And many of the justices have valued confidentiality over transparency and chosen to postpone scrutiny of their work for years to come. In contrast with the executive branch, which is required to preserve and ultimately make public a record of its inner workings, there are no laws to determine what the justices save, shred, burn or reveal, or when.

The court does not share any information about policies or plans for records; a spokeswoman for the court did not respond to written questions. People familiar with the episode after Justice Scalia’s death, who spoke to The New York Times on the condition of anonymity because of the court’s sensitivity over disclosure of internal workings, recalled that a consensus was reached, but had differing memories of its terms and how solid or lasting it was. Still, the death of Justice Ruth Bader Ginsburg, just a few years later, provides a clue: Her Supreme Court papers went, at her direction, to the Library of Congress on the condition that no case file would be opened until every justice involved in the matter had died, a restriction that could lock away many documents for decades.

Though some justices in previous eras arranged for their papers to be released not long after their own deaths, the trend on the Roberts court has been to impose much tighter restrictions, serving to further obscure a branch of government that has resisted calls for more transparency. Each year, the justices carefully compose and edit about 60 opinions in argued cases to share with the world. The fuller, richer narratives of each case, showing the behind-the-scenes stories of how members of the court pressured, persuaded and prevailed over one another to arrive at those opinions, are hidden away in the justices’ working papers — their confidential internal memos and opinion drafts. “There is a story behind every Supreme Court decision,” said Brad Snyder, a legal historian at Georgetown University and the author of a biography of Justice Felix Frankfurter. “Without the papers, we can’t understand it.”The justices have said they want to keep those internal exchanges out of view, contending that secrecy protects the authority and finality of their decisions.

Since Justice Scalia’s death, two members of the court have retired. But neither of them, Justices Anthony M. Kennedy and Stephen G.

Breyer, has announced plans for his papers. Because of the court’s lack of transparency, it is impossible to say what will become of the inner history of its current work — which scholars say is more crucial, and more endangered, than ever. In the decade since 2016, the Roberts...