What if you had your name legally changed, and the new you liked the old you's old work (new at the time for the old you) but the new you wanted to still be the new you while using that same paper you wrote when the new you was still the old you?
But in all seriousness, doesn't the 5th amendment prevent you from self incriminating yourself either way? Yes.
Can't plagiarize yourself, because you can't try to pass off work as your own, unless it's not your own. In other words, nobody gives a ****, and if they do, tell them to get a hobby.