The issue of reporter’s privilege is a very difficult one. My own view is that law enforcement should generally be able to get search warrants to examine material that the press have collected. If law enforcement has probable cause to believe that the materials that the press have collected are relevant to a crime, they should generally be able to look at that material. I believe that this would override any First Amendment right that journalists might have to keep their sources confidential.
The only constitutional issue relating to this question is the First Amendment’s protection of freedom of the press. Congress is not allowed to make any law abridging the freedom of the press. Of course, this is not an absolute guarantee. The press cannot, for example, print libelous articles. Therefore, it is not clear that the right to freedom of the press includes the right to keep sources confidential. Courts have ruled that there is only a limited right to confidentiality. The right to confidentiality has to be balanced against the general interest of society in maintaining law and order.
I do not believe that we would be in danger of losing the freedom of the press if law enforcement could look at journalists’ files. I do not think that there is any huge public interest in journalists being able to investigate crimes without sharing their findings with law enforcement. I believe journalists need to be free to write about things like government corruption, but they do not need to be free to conceal sources that have knowledge about something like a murder.