Cipollone's response to OSC is weird, hysterical and highly personal. I'm surprised by its poor quality. He says he had little time to respond, but a polished one-page placeholder response would have been more effective than this unmoored 11-page rant. This is 2019.
Cipollone argues that OSC lacks regulatory authority (similar to something the WH unsuccessfully tried with OGE), but he's actually taking issue with an advisory opinion. The statute authorizes OSC to issue advisory opinions on the relevant chapter of title 5, U.S.C. (ch. 15).
Cipollone closes by demanding OSC's investigative file, all internal and external correspondence about Conway, and all underlying work papers on which OSC relied. It is likely that OSC and all Inspectors General will (and should) see this is a threat to their independence.
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