In United States v. Brown, --- F.3d ---, No. 16-30143 (9th Cir. 2017), the Court held:
(1) when an inmate serving a federal sentence is transferred to a state institution under a writ of habeas corpus ad prosequendum, he or she remains in “the custody of the Attorney General” -- i.e., in federal custody. Thus, in this case, the defendant could be federally prosecuted for attempted escape from the state institution.
(2) when the government first indicates it does not intend to bring charges, but then receives (unsolicited) a written confession, and thereafter files charges, this does not create a presumption of vindictiveness.
The case also has some interesting stuff for us appellate people.
The Court reminds us that, like other jurisdictional challenges, "the merits of a vindictive prosecution claim are
reviewable even after entry of an unconditional plea because
the defendant is contending that “the very initiation of the
proceedings against him” constitute a denial of the due
process of law."
Also, there is a good fn explaining that, when no facts are at issue, "the question is purely legal."