There is no law that categorically prohibits all leaks of classified (or unclassified) information. Instead, there is a patchwork of statutes that outlaw some unauthorized disclosures under some circumstances.
The various statutes that have been used to punish leaks of classified information are surveyed in a new publication from the Congressional Research Service. See The Law and Leaks to the Press, CRS Legal Sidebar, February 22, 2017.
“Not every leak to the press is a federal crime,” CRS notes. Even when a disclosure is a potential crime, the underlying statutes are not self-activating or self-enforcing. Investigators and prosecutors retain considerable discretion about how to proceed.
Other noteworthy new or updated reports from the Congressional Research Service include the following.
A New Authorization for Use of Military Force Against the Islamic State: Issues and Current Proposals, updated February 21, 2017
Iran’s Nuclear Program: Tehran’s Compliance with International Obligations, updated February 23, 2017
Federal Building and Facility Security: Frequently Asked Questions, updated February 22, 2017
U.S. Secret Service: Selected Issues and Executive and Congressional Responses, updated February 22, 2017
Health Care-Related Expiring Provisions of the 115th Congress, First Session, updated February 22, 2017
El Salvador: Background and U.S. Relations, updated February 23, 2017
The North American Free Trade Agreement (NAFTA), updated February 22, 2017