A principal officer must be confirmed by the Senate. And that has a very significant consequence today.
It means that Mr. Trump’s installation of Matthew Whitaker as acting attorney general of the United States after forcing the resignation of Jeff Sessions is unconstitutional. It’s illegal. And it means that anything Mr. Whitaker does, or tries to do, in that position is invalid.
In times of crisis, interim appointments need to be made. Cabinet officials die, and wars and other tragic events occur. It is very difficult to see how the current situation comports with those situations. And even if it did, there are officials readily at hand, including the deputy attorney general and the solicitor general, who were nominated by Mr. Trump and confirmed by the Senate. Either could step in as acting attorney general, both constitutionally and statutorily.