A lot of things aren't legally "his," Maga pseudo-intellectuals. Like the 2020 election, the authority to send troops to occupy US cities for law enforcement purposes, the right to withhold Congressional funds from universities, to mandate what a semi-private institution like the Smithsonian may or may not exhibit, to use his office to trade in bitcoin - the list goes on. At the end of the day - if he ever leaves office - he'll take it with him. But he believes the whole US government is his, so it was indeed "gifted" to him.
