For individuals and firms who live under federal regulation, actual regulations are just the beginning of the story. Despite being voluminous and complex, regulations leave many matters open to interpretation, and they leave agency officials with discretion over implementation and enforcement. Individuals and firms want to know how the agency reads the ambiguous provisions and how it will use the discretion left it. And officials want individuals and firms to have that knowledge to facilitate voluntary compliance. So officials provide the public with lots of “guidance”: advisories, interpretive letters, enforcement manuals, fact sheets, FAQs, and more. Although ubiquitous, guidance is also controversial. It can be issued without the proces...