Earlier administrations have fired and prosecuted government officials who provided classified information to the media.
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 espionage laws.
Such an approach would signal a revision of the informal rules of engagement that have governed the relationship between the news media and the government for decades. Leaking in Washington is commonplace and typically entails tolerable risks for government officials and, at worst, the possibility of subpoenas to journalists by prosecutors seeking the identities of sources.
But the Bush administration is putting pressure on the news media as never before, and it is operating in a judicial climate that seems increasingly receptive to constraints on journalists.
In the last year, 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 CIA analyst was fired for unauthorized contacts with reporters; and numerous 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. Administration officials have said that the law allows such prosecutions and that they will use their prosecutorial discretion in this area judiciously.
A Justice Department spokeswoman, Tasia Scolinos, declined to comment Friday.
Such prosecutions of reporters are unprecedented in the U.S. But legal experts say that the law may allow holding journalists accountable for crimes. Should the administration pursue the matter, these experts say, it could gain a tool that would alter the balance of power between the government and the news media.
The administration and its allies say 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, Sen. John Cornyn, a Texas Republican, asked Attorney General Alberto R. Gonzales whether the government's investigation into The Times' disclosure of a National Security Agency eavesdropping program included "any potential violation for publishing that information."
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."
One example of the administration's new approach is the FBI'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 this month, "no private person may possess classified documents that were illegally provided to them."
Critics of the administration position say altering the conventional understanding between the news media 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."
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 news media. But two of the justices in the 6-3 majority indicated that there was a basis for after-the-fact prosecution of the newspapers that published the papers under espionage laws.
Critics and allies of the current administration say that espionage laws may be read to forbid possession and publication of classified information by the news media. Two provisions are at the heart of the recent debates.
The first, enacted in 1917, is "at first blush, pretty much one of the scariest statutes around," according to a 2002 report by Susan Buckley, a lawyer who often represents news organizations.
It prohibits anyone with unauthorized access to documents or information concerning 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 that "it seems undeniable that a newspaper" can be "vulnerable to prosecution" under the 1917 law.
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 9/11, said that The Times, for its disclosures about the NSA domestic spying program, and The Washington Post, for an article about secret CIA prisons, have violated the 1917 law. The Times, he said, has also violated the 1950 law.
"It was irresponsible to publish these things," McCarthy said. "I wouldn't hesitate to prosecute."
The reporters who wrote the 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.