Copernicus
Industrial Grade Linguist
This argument isn't quite as easy as that, as the Government was pretty clear in informing him he had no legal right to these docs. But it is an argument his lawyers can make.
Such arguments might work if there is a strong MAGA loyalist on the jury, but I think Trump is counting on tying the trials up until after the election next year or until he and his allies find ways to wreck the prosecutions. He stands a reasonable chance of doing that. I don't see him being the slightest bit deterred from trying to intimidate witnesses and potential jurors. It's possible some of his supporters will resort to violence against judges and prosecutors.