Eight US newspapers and the Associated Press agency have thrown their support behind three bloggers sued by Apple.
Apple won the right to make bloggers reveal sources in March
In March, Apple won the right to see the bloggers' e-mail records to find out who leaked information on upcoming products to them, which they published.
The news organisations have now filed a court brief which says they should be allowed to protect their sources.
If not, they said, it could make journalists wary of publishing stories which are in the public interest.
Sources who give journalists details of corruption or wrongdoing are traditionally protected by law, if the story is in the public's interest.
"Recent corporate scandals involving WorldCom, Enron and the tobacco industry all undoubtedly involved the reporting of information that the companies involved would have preferred to remain unknown to the public," said the brief.
Dave Tomlin, assistant general counsel for the AP news agency, said the case had potential implications journalists of all kinds.
"For us, this case is about whether the First Amendment protects journalists from being turned into informants for the government, the courts or anybody else who wants to use them that way," Mr Tomlin said.
"We believe strongly that it does, and that it's a good thing for all of us that journalists have this protection."
Apple spokesperson, Steve Dowling, said: "Apple's DNA is innovation, and protection of trade secrets is crucial to our success."
It filed lawsuits in the California courts in December 2004 against individuals it said had leaked trade secrets about the Asteroid music product.
The lawsuit to force the websites to reveal the names of the sources was filed against Power Page and Apple Insider.
The information appeared on three Apple enthusiast websites, PowerPage, Apple Insider and Think Secret.
Last month's ruling by Santa Clara County Superior Court Judge James Kleinberg meant the bloggers' net providers would have to hand over e-mail records. Apple fiercely guards its upcoming products and has taken legal action before.
The online authors of the sites said the ruling would create a "chilling effect" on journalism as a whole.
In their court submission, the media organisations said that Apple should "exhaust all alternative sources" before making the net service providers turn over e-mail records.