Stephen Migala (Government of the United States of America) has posted The Foreign Affairs Function and the APA on SSRN.  Here is the abstract:

Federal agency rulemaking is governed by the requirements of the Administrative Procedure Act (APA), which mainly requires public notice-and-comment and a delayed effective date. Sometimes that can be a fast process; other times it can take months or even years. However, a longstanding exception to those APA requirements called the “foreign affairs function” allows qualifying regulations to be immediately issued and effective. But as agencies have increasingly used this exception, its use has been increasingly challenged by litigants. Between these growing disputes, and with little history and context to guide them, courts have been confused as to what qualifies under the exception. And an intra- and inter-circuit split is slowly emerging over the meaning of “foreign affairs.” But history and context for this exception does exist. This article uniquely traces its previously unknown origins over a ten-year history to illuminate its source, development, and contemporaneous understandings.