Earlier administrations have fired and prosecuted government officials who provided classified information to the press. They have also tried to force reporters to identify their sources.
But the Bush administration is exploring a more radical measure to protect information it says is vital to national security: the criminal prosecution of reporters under the espionage laws.
Such an approach would signal a thorough revision of the informal rules of engagement that have governed the relationship between the press and the government for many decades. Leaking in Washington is commonplace and typically entails tolerable risks for government officials and, at worst, the possibility of subpoenas to journalists seeking the identities of sources.
But the Bush administration is putting pressure on the press as never before, and it is operating in a judicial climate that seems increasingly receptive to constraints on journalists.
In the last year alone, a reporter for The New York Times was jailed for refusing to testify about a confidential source; her source, a White House aide, was prosecuted on charges that he lied about his contacts with reporters; a C.I.A. analyst was dismissed for unauthorized contacts with reporters; and a raft of subpoenas to reporters were largely upheld by the courts.
It is not easy to gauge whether the administration will move beyond these efforts to criminal prosecutions of reporters. In public statements and court papers, administration officials have said the law allows such prosecutions and that they will use their prosecutorial discretion in this area judiciously. But there is no indication that a decision to begin such a prosecution has been made. A Justice Department spokeswoman, Tasia Scolinos, declined to comment on Friday.
Because such prosecutions of reporters are unknown, they are widely thought inconceivable. But legal experts say that existing laws may well allow holding the press to account criminally. Should the administration pursue the matter, these experts say, it could gain a tool that would thoroughly alter the balance of power between the government and the press.
The administration and its allies say that all avenues must be explored to ensure that vital national security information does not fall into the hands of the nation's enemies.
In February, Senator John Cornyn, Republican of Texas, asked Attorney General Alberto R. Gonzales whether the government's investigation into The Times's disclosure of a National Security Agency eavesdropping program included "any potential violation for publishing that information."
Mr. Gonzales responded: "Obviously, our prosecutors are going to look to see all the laws that have been violated. And if the evidence is there, they're going to prosecute those violations."
Recent articles in conservative opinion magazines have been even more forceful.
"The press can and should be held to account for publishing military secrets in wartime," Gabriel Schoenfeld wrote in Commentary magazine last month.
Surprising Move by F.B.I.
One example of the administration's new approach is the F.B.I.'s recent effort to reclaim classified documents in the files of the late columnist Jack Anderson, a move that legal experts say was surprising if not unheard of.
"Under the law," Bill Carter, a spokesman for the Federal Bureau of Investigation, said earlier this month, "no private person may possess classified documents that were illegally provided to them."
Critics of the administration position say that altering the conventional understanding between the press and government could have dire consequences.
"Once you make the press the defendant rather than the leaker," said David Rudenstine, the dean of the Benjamin N. Cardozo School of Law in New York and a First Amendment scholar, "you really shut down the flow of information because the government will always know who the defendant is."
Reading of Espionage Laws
The administration's position draws support from an unlikely source — the 1971 Supreme Court decision that refused to block publication by The Times and The Washington Post of the classified history of the Vietnam War known as the Pentagon Papers. The case is generally considered a triumph for the press. But two of the justices in the 6-to-3 majority indicated that there was a basis for after-the-fact prosecution of the newspapers that published the papers under the espionage laws.
Both critics and allies of the administration say that the espionage laws on their face may well be read to forbid possession and publication of classified information by the press. Two provisions are at the heart of the recent debates.
The first, enacted in 1917, is, according to a 2002 report by Susan Buckley, a lawyer who often represents news organizations, "at first blush, pretty much one of the scariest statutes around."
It prohibits anyone with unauthorized access to documents or information concerning the national defense from telling others. The wording of the law is loose, but it seems to contain a further requirement for spoken information. Repeating such information is only a crime, it seems, if the person doing it "has reason to believe" it could be used "to the injury of the United States or to the advantage of any foreign nation." That condition does not seem to apply to information from documents.
In the Pentagon Papers case, Justice Byron R. White, joined by Justice Potter Stewart, said "it seems undeniable that a newspaper" can be "vulnerable to prosecution" under the 1917 law.
Indeed, the Nixon administration considered prosecuting The Times even after the government lost the Pentagon Papers case, according at a 1975 memoir by Whitney North Seymour Jr., who was the United States attorney in Manhattan in the early 1970's. Mr. Seymour wrote that Richard G. Kleindienst, a deputy attorney general, suggested convening a grand jury in New York to that end. Mr. Seymour said he refused.
Some experts believe he would not have won. The most authoritative analysis of the 1917 law, by Harold Edgar and Benno C. Schmidt Jr. in the Columbia Law Review in 1973, concluded, based largely on the law's legislative history, that it was not meant to apply to newspapers.
A second law is less ambiguous. Enacted in 1950, it prohibits publication of government codes and other "communications intelligence activities." Andrew C. McCarthy, a former federal prosecutor who took part in terrorism investigations in New York after the Sept. 11 attacks, said that both The Times, for its disclosures about the N.S.A. program, and The Post, for an article about secret C.I.A. prisons, have violated the 1917 law. The Times, he added, has also violated the 1950 law.
"It was irresponsible to publish these things," Mr. McCarthy said. "I wouldn't hesitate to prosecute."
The reporters who wrote the two articles recently won Pulitzer Prizes.
Even legal scholars who are sympathetic to the newspapers say the legal questions are not straightforward.
"They are making threats that they may be able to carry out technically, legally," Geoffrey R. Stone, a law professor at the University of Chicago and the author of "Perilous Times: Free Speech in Wartime," said of the administration. The law, Professor Stone added, "has always been understood to be about spying, not about newspapers, but read literally it could be applied to both."
Others say the law is unconstitutional as applied to the press under the First Amendment.
"I don't think that anyone believes that statute is constitutional," said James C. Goodale, who was the general counsel of The New York Times Company during the Pentagon Papers litigation. "Literally read, the statute must be violated countless times every year."
Rodney A. Smolla, the dean of the University of Richmond law school, took a middle ground. He said the existing laws were ambiguous but that in theory it could be constitutional to make receiving classified information a crime. However, he continued, the First Amendment may protect newspapers exposing wrongdoing by the government.
The two newspapers contend that their reporting did bring to light important information about potential government misconduct. Representatives of the papers said they had not been contacted by government investigators in connection with the two articles.
That is baffling, Mr. McCarthy said. At a minimum, he said, the reporters involved should be threatened with prosecution in an effort to learn their sources.
"If you think this is a serious offense and you really think national security has been damaged, and I do," he said, "you don't wait five or six months to ask the person who obviously knows the answer."
Case Against 2 Lobbyists
Curiously, perhaps the most threatening pending case for journalist is one brought against two former lobbyists for the American Israel Public Affairs Committee, or Aipac. The lobbyists, Steven J. Rosen and Keith Weissman, were indicted in August on charges of violating the 1917 law by receiving and repeating national defense information to foreign officials and reporters.
The lobbyists say the case against them is functionally identical to potential cases against reporters.
"You can't say, 'Well, this is constitutional as applied to lobbyists, but it wouldn't be constitutional if applied to journalists,' " Abbe D. Lowell, a lawyer for Mr. Rosen, said at a hearing in the case last month, according to a court transcript.
In court papers filed in January, prosecutors disagreed, saying lobbyist and journalist were different. But they would not rule out the possibility of also charging journalists under the law.
"Prosecution under the espionage laws of an actual member of the press for publishing classified information leaked to it by a government source would raise legitimate and serious issues and would not be undertaken lightly," the papers said. Indeed, they continued, "the fact that there has never been such a prosecution speaks for itself."
Some First Amendment lawyers suspect that the case against the lobbyists is but a first step.
"From the point of view of the administration expanding its powers, the Aipac case is the perfect case," said Ronald K. L. Collins, a scholar at the First Amendment Center, a nonprofit educational group in Virginia. "It allows them to try to establish the precedent without going after the press."