There is longstanding support for confidentiality of sources or reporter’s privilege, even in international law:
Simply put, it means that the authorities, including the courts, cannot compel a journalist to reveal the identity of an anonymous source for a story. The right is based on a recognition that without a strong guarantee of anonymity, many people would be deterred from coming forward and sharing information of public interests with journalists. As a result, problems such as corruption or crime might go undetected and unchallenged, to the ultimate detriment of society as a whole.
But now a U.S. Federal Appeals Court has determined that doesn’t matter:
The three judges in the Fourth U.S. Circuit Court of Appeals have ruled that neither the First Amendment, nor a significant body of case laws concerning the protection of anonymous sources used by investigative journalists. will save James Risen from having to testify in the case of Jeffery Sterling. While most journalists are acutely aware of the current climate for whistleblowers and leakers of state secrets, this decision will likely further discourage potential sources from seeking out journalists to tell their stories and establishes a very worrying precedent.
At what point does the law actually matter?
If whistleblowers have no protection, as seems to be the case with this ruling. what is the likelihood that we will ever hear of problems occurring? Next to none I’d guess.