Journalists are generally discouraged by their colleagues from appearing before Congressional committees, and they’re strictly forbidden from lobbying Members. In turn, reporters are given nearly unfettered access of the Capitol to ply their trade, while visitors and influence peddlers are limited to the public hallways.

The idea is to establish a rock-solid wall, ensuring that readers are not forced to determine if a story is biased.

But in rare instances, when the issue at hand involves protecting the media’s rights, those restrictions go out the window. And today marks one of those occasions.

When several media types appear before the Senate Judiciary Committee today to lobby for legislation that would shield reporters from being forced to disclose their sources, it will be with the blessing of the committees that oversee the credentialing of the Capitol Hill press corps.

Time Inc. editor in chief Norman Pearlstine, Time magazine White House Correspondent Matthew Cooper and former New York Times political columnist William Safire are all scheduled to appear before the Judiciary panel this morning to discuss the bipartisan legislation designed to protect journalists from prosecution.

Floyd Abrams, the lawyer representing jailed New York Times reporter Judith Miller, was a late addition to the witness list and is also expected to appear before the panel. Abrams did not return telephone calls Tuesday regarding his testimony.

While three separate committees of journalists — each with a distinct set of rules — have jurisdiction over the daily, weekly and broadcast media, they all support preserving principles they see as necessary to keeping freedom of the press alive and the government in check.

“The public has a vested interest in the press defending the press,” said Lorraine Woellert, a BusinessWeek reporter who serves as the chairwoman of the Executive Committee of Correspondents, the panel that governs periodical publications.

The hearing comes as the news media is being forced to re-evaluate how it operates after Miller was jailed for refusing to reveal the person who told her that Valerie Plame, the wife of former diplomat and Bush administration critic Joe Wilson, was a CIA operative.

Cooper avoided going to jail for contempt of court after White House Deputy Chief of Staff Karl Rove, Cooper’s source on the Plame matter, released him from the confidentiality agreement.

“I am going to join several other witnesses in advocating a national shield law to protect whistle-blowers and other confidential sources,” Cooper said in an interview Tuesday. “Forty-nine states have some kind of legal protection for journalists and confidential sources, but there is no such protection at the federal level. Democrats and Republicans in Congress are looking for a way to correct this asymmetry.”

When asked if he would discuss Rove, Cooper said his appearance before Congress was to talk about the legislation.

Bills have been introduced in both the House and Senate to protect journalists. Sen. Chris Dodd (D-Conn.), a co-author of the Senate legislation, said it is absolutely necessary for Congress to act on this issue.

“This bill is really, with all due respect, not about reporters,” Dodd said. “It has far more to do with the consumers of information than the producers of information. As a consumer of information, if we are denied an opportunity to find things out we all suffer.”

Without specifically naming Patrick Fitzgerald, the prosecutor who has been aggressively pursuing the Plame leak case, Dodd criticized federal prosecutors for turning immediately to reporters for information about their cases instead of working harder to ascertain facts independently.

“The problem with these prosecutors is the first arrow they draw from their quiver is to go after the reporter rather than doing the hard work of exploring other avenues to determine if leaks of information are critical to national security,” said Dodd, who added that he does not think Miller should be incarcerated.

Sen. Lindsey Graham (R-S.C.), a co-sponsor of the Free Flow of Information Act, echoed Dodd’s assessment that reporters need to be allowed to protect their sources.

“I think a free press able to get information about what is going on in the government in a responsible fashion is good for the country,” said Graham. “Whether you are liberal or conservative, it is good to know what your government is up to.”

Given all the attention likely to be devoted to the upcoming confirmation hearings on a successor to retiring Supreme Court Justice Sandra Day O’Connor, it is not clear whether the Senate will vote on the the legislation this year. But Dodd suggested several legislative vehicles to which it could be attached as an amendment, such as the Defense authorization bill.

“If we are going to get something done, this may be the year to do it,” Dodd said.