

Executive orders can only instruct the Executive Branch to take some sort of action. While the Department of Justice is a part of the Executive Branch, it consists of the government’s lawyers, not of the government’s judges. The judicial branch is outside the purview of the Executive Branch, and so out of reach of a Trump EO.
Now, would he still try? Of course he would. But it would have the same legal weight as Michael Scott yelling “I DECLARE BANKRUPTCY!!”
He can do it, but it won’t matter. EOs directed at something outside of the Executive Branch are basically just announcements.