When an existing administration steps down and an ideologically opposed one takes over, do those secret treaties every government must occasionally be forced to make get communicated to the new boss? This sort of international intercourse used to have some continuity, that's why we have a State Department, but today most international relations are conducted directly from the White House, often in secret, and there is no reason a departing administration couldn't make things unpleasant for a new one by simply not telling it everything it was up to--especially if it was potentially embarassing.