In 2006, two California reporters were facing 18 months in prison unless they revealed who slipped them grand jury information about a nutritional supplement maker named Bay Area Laboratory Co-operative, better known as BALCO. They avoided incarceration when their source outed himself, but the reporters never confirmed it, refusing to renege on their promise of confidentiality.

At that time, the story was mostly about baseball slugger Barry Bonds and his suspected steroid use. But it led to an investigation directed by George Mitchell, a former U.S. senator and federal judge, and, last week, a tense congressional hearing featuring testimony by star pitcher Roger Clemens. The issue might have unfolded as it has, no matter what some California reporters did. But maybe the persistent enterprise of an independent press is what kept the powerful stakeholders involved from keeping a lid on how pervasive the use of performance-enhancing substances is.

What-if questions have no certain answers. But effective self-government is impossible if government and other influential institutions have tools to thwart independent inquiry.

At present, New York Times reporter James Risen may be headed toward a predicament like the one the California reporters faced. A grand jury in Virginia wants him to reveal the source for his 2006 book outlining attempts by the CIA, going back to the Clinton administration, to infiltrate Iran’s nuclear program.

“Every government has an interest in concealment,” wrote philosopher Sissela Bok, “every public in greater access to information.”

That public access often happens only because there was an insider willing to risk breaking the code of silence. In cases ranging from steroids to the CIA, reporters who assure those sources confidentiality take that risk upon themselves. Neither sources nor journalists should have to forfeit their freedom for the public to hear the truth.

Fortunately, a growing number of state and federal lawmakers are lining up behind shield laws that allow reporters to protect their sources. Last year, Washington became the 32nd state, plus the District of Columbia, to grant such protection. Now a bipartisan federal shield law has cleared the House by a comfortable 398-21 margin. It allows reporters to protect sources, but makes reasonable exceptions in situations genuinely involving public safety, national security, trade secrets, and personal health and financial information.

U.S. Rep. Mike Pence, an Indiana Republican known for harsh criticism of the press, is a leading congressional advocate of the law. Coming from a state that has had a shield law since 1941, Pence stresses that it is a necessary instrument of accountability. It’s now the Senate’s turn to act responsibly on this overdue measure.

In the words of Lance Williams, one of the San Francisco Chronicle reporters in the BALCO story, “Every time we get a subpoena … the closer we get to the day when the only information we’ll have about our government is from the paid story-spinner.”