Liability of the New Commander for Crimes of the Previous One

One of our doctoral students, David Akerson, has asked for feedback, comments, ideas, suggestions, state practice, etc, on the issue of successor superior/subordinate liablity. the issue arises with respect to the new President. Does Obama have a duty under international law to punish subordinates he inherits from Bush if he knows (or has reason to know) that they have committed crimes.
Some relevant precedent he refers to:
The statutes of the international criminal tribunals, the relevant texts of which are derived from Additional Protocol I, articles 86 and 87. The language in these two provisions is conflicting; one uses present tense language and the other past tense. Present tense language (duty to punish crimes a superior knows his subordinates are committing) would argue against Obama having a duty. Past tense (duty to punish crimes a superior knows his subordinates have committed) would argue in favor of it.
Hadzihasanovic was indicted as a successor commander at the ICTY, and the Appeals Chamber found that the duty to punish, set out in article 7(3) of the Statute, did not extend to commanders for crimes committed by subordinates before the commander assumed command. However, it was a 3-2 decision, with judges Hunt and Shahabadeen issuing what David says were compelling dissents.
The Tadic trial chamber in dicta indicated that liability would extend to successor commanders.
The Rome Statute's version of Superior / Subordinate liability (art. 28) uses the present tense and thus excludes successor liability. The commentary indicates (with a note of irritation) that this creates the proverbial lacuna.
US Army Field Manual 27-10 para. 501 uses the past tense seeming to support successor liability.