With the House passage of a media shield bill yesterday, reporters across the country secured a legislative victory most were too uncomfortable to actually ask for.

The measure, which passed 398-21, protects reporters from prosecution and possible jail time for refusing to disclose their sources, with certain exemptions for national security, trade secrets and personal health information. A similar measure cleared the Senate Judiciary Committee earlier this month, but the bill faces a veto threat from the White House.

The bill puts the Fourth Estate in a tricky spot: while most reporters agree that the protection the bill offers is an undeniably good thing, it also forces them to decide whether it’s appropriate to act as advocates in a legislative process they are trained to observe, not to join.

Clint Brewer, president of the Society of Professional Journalists, an education and advocacy group for reporters, acknowledged the awkwardness of asking journalists to lobby. He said his group has tried to limit requests that its members contact lawmakers.

“We don’t really ask our rank and file to lobby, because its uncomfortable territory for some,” he said. “We’re not asking people to heat up people’s phone lines. We mainly take that on ourselves as folks leading the organization.”

But the issue is featured front and center on the group’s Web site, under a banner reading “Struggling to Report” over a photo of cuffed hands. Further down, the page encourages members to “contact your local representative TODAY to let them know you support a federal shield law” and to “write stories about the importance of this bill’s passing, or encourage your news team to draw attention.”

Rep. Mike Pence (R-Ind.), a former radio broadcaster and original sponsor of the House law, recognized the difficulty reporters might have speaking up for themselves. In a video posted on SPJ’s Web site, he recommends “Maybe it would be more comfortable if you encouraged members around the country, not so much to advocate for a piece of legislation but as much as to write a column or explain how they do what they do.”

In the last year alone, about 120 editorial pages across the country have answered the call by coming out in favor of the law, said John Sturm, president of the Newspaper Association of America.

Editorialists often qualified their support with the disclosure that their parent company has been spending money to lobby the measure — or, in other cases, by noting that the exceptional circumstances facing journalists are compelling them to cross a line they ordinarily wouldn’t.

“As a general rule, journalists shouldn’t be in the business of lobbying Congress,” Jonathan Alter wrote in Newsweek in 2005. “But once in a long while an issue comes along that so threatens what we do — and what you read and see — that we need to use whatever leverage we have to change the law.”

After a 1972 Supreme Court decision invalidated the First Amendment as a defense for reporters called to testify before a grand jury, states moved quickly to adopt shield laws. Today, 31 states and the District of Columbia have shield laws, according to the Reporters Committee for Freedom of the Press.

National media organizations avoided pressing for a federal law, meanwhile, because they didn’t seem to need one. But a recent pile-up of court cases in which prosecutors tried to use the threat of jail time to force reporters to reveal confidential sources has helped turn the tide.

Most famously inside the Beltway, on July 6, 2005, New York Times reporter Judith Miller was sentenced to jail for refusing to name her source in the Valerie Plame leak investigation.

That day, the board of the American Society of Newspaper Editors voted to endorse a federal shield law. Only two members of the 20-person board objected, ASNE Executive Director Scott Bosley said.

“There is a basic reticence among editors to be in a position of lobbying for anything that they cover,” he said. “But we reached a point where the courts were not the resort they had been for us and we felt we had to do something legislatively.”

Two weeks later, Time magazine’s Matt Cooper, who narrowly avoided jail in the same case after he said his source released him from their confidentiality agreement, took the rare step of testifying before the Senate Judiciary Committee.

“We need some clarity,” he told the Senate panel. “As a working journalist, I’d like to know better what promises I can legally make and which ones I can’t.”

Lawmakers on both sides of Capitol Hill introduced media shield laws that year, but none made it out of committee during the GOP-led 109th Congress. Republican leadership objected to the bills on the grounds they could stymie Justice Department investigations with consequences for national security.

The Democratic takeover — and additional prosecutions of reporters trying to protect their sources — breathed new life into shield law proposals this year.

Lance Williams and Mark Fainaru-Wada, San Francisco Chronicle reporters who narrowly escaped prison sentences this year after rebuffing a prosecutor’s demands they disclose sources from their BALCO steroid investigation, have become the bill’s most outspoken reporter-advocates.

Williams said the decision to lobby on behalf of the bill was a no-brainer. “If the press won’t stand up for the people’s First Amendment rights, who is going to do it?” he said. “This is not a hypothetical situation. This is a crisis.”

Williams said he already has made three visits to the Hill to talk up the proposal with Members and staff — and he’d be happy to return. “I’ll talk to six people on a street corner to get it passed, because I think it’s that important.”

Journalists equally anxious for a federal shield but uneasy saying so publicly can rely on a more traditional lobbying coalition pushing the bill.

The informal alliance, coordinated by the Newspaper Association of America, includes trade associations like the Magazine Publishers of American and the National Association of Broadcasters in addition to such media giants as Clear Channel, Gannett, News Corp and The New York Times Co.