I disagree with @neal_katyal & @gtconway3d (to my mind, temporary “assignments” to offices aren’t the same thing as formal “appointments” for purposes of the Appointments Clause), but this is an important read and something that’s sure to be litigated:
https://www.nytimes.com/2018/11/08/opinion/trump-attorney-general-sessions-unconstitutional.html …
How's this going to interact with all the legal arguments about Muller's authority (ala Calabresi)? Now he doesn't have a "proper" principal officer overseeing him anymore?