The topic of “secret law” is probed at great length in a new law review paper, which substantiates the concept and suggests a set of principles for addressing it. See “Coming to Terms with Secret Law” by Dakota S. Rudesill, to be published in the Harvard National Security Journal.
Secret law is defined here as “legal authorities that require compliance [but] that are classified or otherwise withheld from the public.”
The paper provides extensive citations to relevant source material (including a few references to Secrecy News), thoughtful consideration of arguments for and against the status quo, and a novel compilation of congressional reports that include classified addenda. (h/t Lawfare)