There is a well-established but uneven pattern in American law that applies to government secrets and the journalists who uncover them. The First Amendment generally protects the publication of a leak, but not the leaker.

An authority no less than the Supreme Court has made it this way. In 1971, as the justices prepared to rule that the government could not prevent The New York Times from publishing the Pentagon Papers — one of the biggest leak cases in history — the source of that leak, Daniel Ellsberg, was indicted by a federal grand jury for theft.

The court is now grappling with one of the most significant disclosures of a government secret since then: the release of a draft opinion that sets the framework for overturning Roe v. Wade.

Only this time the leak came from inside the building. And there is no law or written code of conduct that suggests how an investigation into such a breach should proceed, or whether the journalists at Politico who brought the draft to light will be swept up in the kind of criminal investigation that top Republican lawmakers have demanded.

Unlike the Pentagon Papers, the government study of the country’s involvement in Vietnam, the draft opinion was not classified information. Leaking classified information is a crime. Instead, the recent leak broke the Supreme Court’s conventions for secrecy, an offense that has been punishable with almost certain career death but little else.

Given the magnitude of the leak and the aggressiveness with which federal prosecutors have pursued high-profile leakers and journalists in recent years, a criminal investigation is not unthinkable, legal experts said. And while no one is suggesting that Politico broke any laws in the course of publishing its article about the draft opinion, that does not mean the journalists involved would be spared from government pressure to reveal their sources if a grand jury was convened to consider charges against the leaker.

“I think it’s pretty clear there is at least enough for a grand jury to investigate,” said Eugene Volokh, a First Amendment expert at the University of California, Los Angeles, law school. “The interesting question is to what extent there’s going to be a subpoena to a reporter.”

Often the government will decline to pursue journalists, Mr. Volokh added, noting how that could end up happening case here. But as a legal matter, he said, “I think subpoenaing the reporter would be constitutional.”

Media outlets and federal prosecutors have for decades been at loggerheads over whether journalists can be forced to reveal their sources in criminal leak investigations. In recent cases, the Justice Department has obtained phone records and emails from reporters at The Associated Press, Fox News, The Times and other outlets in pursuit of leakers. Many of those cases involved the release of classified information.

The Supreme Court is an institution that prides itself on a strict, lawyerly but ultimately nonbinding adherence to confidentiality.

That has been enough to make the court the most impenetrable of the government’s three branches, its inner workings shrouded in secrecy and mostly absent from the bombshell tell-alls that are part and parcel of Washington journalism. (There have been some notable exceptions over the years, including a strikingly similar leak in 1973 to Time of the details of the Roe decision before it was announced.)

“I’m not sure they have a guidebook for what the next step is going to be. I don’t think anyone does,” said Sonja West, a law professor at the University of Georgia who was a clerk for Justice John Paul Stevens. Ms. West did not defend the leak, but she did express concern about how far the investigation could go and whether “the next step is Politico and the press,” she said.

“We’re starting to get on First Amendment ice here,” Ms. West added. “And we need to keep that sturdy, and not let it get so thin that we start to see cracks.”

Chief Justice John G. Roberts Jr. has announced an internal inquiry that will be led by the marshal of the court. So far, the Justice Department does not appear to be involved. The court did not respond to a request for comment. Politico, asked whether it anticipated a subpoena and how it would respond to one, declined to comment.

Though the source is only the subject of speculation at this point, many of the guesses have focused on the clerks, given that they make up the bulk of the few dozen people who would have had authorized access to the leaked document. Each justice typically hires four for each term that begins in October, meaning there are usually 36 at any given time. (Beyond them, the nine justices and their personal assistants would also have had access to the draft, people familiar with the court’s processes said.)

It is not exactly a secret that clerks have been anonymous sources for journalists writing about the court over the years. Sometimes they have written books themselves. But clerks do so at great peril for their professional reputations. And most do not leak.

In interviews, former clerks described feeling anxious to the point of paranoia about being suspected of talking to a reporter. One recalled a “20-second rule”: that a clerk shouldn’t be seen in conversation with a reporter in line in the court’s cafeteria or hallways for more than 20 seconds. Some said they had been nervous about expressing too much emotion in the court’s public spaces — like smiling or otherwise appearing in a good mood — for fear that it would give away an outcome their justice favored in a particular case.

Another former clerk recalled being so wary of revealing internal protocol that even today he thought describing what was verboten might be risky.

“I need to remember what is public about the confidentiality rules and what’s not,” the former clerk, Orin Kerr, a law professor at the University of California, Berkeley, said only half jokingly.

Ms. West said she still remembered how Chief Justice William H. Rehnquist’s lecture about confidentiality on her first day had made “your blood run cold.”

One former clerk recalled, in an interview on the High School SCOTUS blog, Justice Antonin Scalia’s stern admonition to his new class of clerks on their first day. “If I ever discover that you have betrayed the confidences of what goes on in these chambers,” the former clerk, Ian Samuel, quoted Justice Scalia as saying, “I will do everything in my power to ruin your career.”

“The norms of confidentiality at the court, they’re not gentle or subtle,” said Allison Orr Larsen, a professor at William and Mary Law School who clerked for Justice David H. Souter. “They are strongly and repeatedly emphasized.”

As blunt and terrifying as those warnings may be, they are informal. So are the rules that apply to the justices themselves, who have been resistant to being bound by written procedures on most matters concerning their work.

“They don’t even have written ethics rules for the justices,” said Paul M. Smith, a law professor at Georgetown University who clerked for Justice Lewis F. Powell Jr. The leak, he said, and the focus on the lack of those standards after recent revelations about the political activities of Virginia Thomas, the wife of Justice Clarence Thomas, may put more pressure on the court to accept new restrictions on how it operates.

Other legal scholars, including some at the conservative Heritage Foundation, have pointed to a number of laws that could be used to prosecute the leaker and spur the kind of wide-ranging investigation that could entangle the press, court staff and even individual justices. One law that has been used against leakers, according to John Malcolm, a legal expert with the Heritage Foundation, broadly deals with theft, embezzlement and the conversion of “things of value” that belong to the government.

None are slam dunks. But First Amendment experts said they would not be surprised if one of these laws was tested in this case.

RonNell Andersen Jones, a professor at the University of Utah’s S.J. Quinney College of Law who clerked for Justice Sandra Day O’Connor, said that when she and a group of former clerks who text one another heard of the Politico article, their immediate reaction was that it had to be a hoax. A leak of this magnitude, they all understood, is strictly forbidden.

“What it means to be strictly forbidden is about to be tested,” Ms. Andersen Jones added.