GH, you mention specific declassification regulations, my Dershowitzian argument is that president can use his own procedure. The only problem would be if he were to take anything after 1200 on the inauguration day or maybe after the new guy takes a shvuye. I think a ganav acquires movables when he picks it up with the intent to take it even while still on property of the baal habait. In this case, T was still baal habait lavan when he picked them up and had declassification powers.
Again, if he were to sneak in later while new guy was sleeping at the wheel as usual, T would be hayav. I am sure this is discussed in halochos of renting real estate somewhere