Unfortunately, I think this will get stopped by the courts. The constitution give the states the authority to conduct elections.
In article 1:
"The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators."
In article 2:
"Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors, equal to the whole Number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or Person holding an Office of Trust or Profit under the United States, shall be appointed an Elector."
Nowhere does it give the president the authority to decide the manner in which these procedures are carried out. To me this means that the states can establish how elections are conducted, including the choice of using mail-in ballots. I am not sure how the president can change this under the constitution. It seems at the very least, congress would have to pass a bill banning mail-in voting. And congress should do this immediately.
