The purpose of the California shield law is not to protect journalists so much as it is to protect sources. What the law states is that a warrant is not sufficient to search and seize a journalist’s (work) property. A subpoena is necessary because it gives the journalist a chance to appear in front of a judge before the information is turned over to investigators and make a case as to what property pertains to the case and what doesn’t.
This is to prevent “newsroom seizures”, in which a newsroom is raided under a warrant and all property within is seized. Why does this matter? Because newsrooms (or in today’s world journalists’ work computers) are sure to contain tons of confidential information regarding completely unrelated to the iPhone case. In this case Mr. Chen very likely may have emails from leakers of trade secrets, corporate whistleblowers, etc. Anything detailed by a source as illegal in an email or other document the police would be required to act upon even if it didn’t have anything to do with the case at hand, thus compromising the journalist’s sources. The ability of a journalist to do his or her job hinges on his or her ability to build trust with confidential sources. The possibility that they might be given up in the course of a completely unrelated investigation would be a huge roadblock for any journalist seeking sensitive information. Thus, California law states that a subpoena is necessary to seize work-related property from a journalist, and why the warrant used to seize Mr. Chen’s property appears to indeed be invalid. (This is why Grand Jury leaks of journalist’s sources are important and troubling.)
