Shield laws are an important mechanism to protect a free and useful press. Shield laws give journalists a range of protection (varying by state) against having to testify in court if doing so reveals confidential information. This protects journalistic integrity and helps maintain trust between sources and journalists, allowing information (even information government wished were confidential) to flow freely. Press censorship and control is one of the first signs of a despotic government, and (surprisingly) the Supreme Court has consistently affirmed freedom of the press.
Shield laws don’t pose a danger to government or society either. It’s not common that reporters have crucial information on criminal cases, as confidentiality is more often an issue with small-crime (like drugs or immigration), political, or celebrity sources. Shiled laws protect the ability to discover and convey information about government, essential to the free democracy America is. It’s more important to preserve this unique American freedom than to make available protected information in any particular trial. Even as seemingly critical an issue as who revealed the identity of Valerie Plame is important only on a political or perhaps military level and does not threaten the nature of American society. Changes in America have not been the direct result of political or international events, but rather the American people’s reaction to them. Some seemingly all-important events have gone practically unnoticed; while others of lesser importance have precipitated sea changes in American society.
Curiously, shield laws arose through an ostensible loophole in a Supreme Court decision (unidentified by Remy) saying that journalists were not ‘shielded’ unless states or the federal government said otherwise. Like other protections, shield laws have spread piecemeal and are now practiced in 36 states and DC.