@Bigun
Just out of curiosity,WHO made this seem like it is suddenly a good idea,after all the decades of not allowing it.
BTW,just because something isn't explicitly legal doesn't mean it is a good idea. If it had been a good idea,our Founding Fathers,who NO sane person can suggest were not a HELL of a lot smarter AND more honest that the creatures we now have in government,would have agreed to this back in the 1776,when it was a HELL of a lot harder for voters to get to the polls than it is today.
In line with the US Constitution, if those powers were not expressly delegated to the Federal Government, it did not have them (they were reserved to the States and the People).
If it didn't say it could, then it couldn't. That was clarified in The Bill of Rights, and later muddled by the courts as often as clarified further.
Perhaps the problem arises from the concept that people could show up in person and vote more cheaply than posting a vote in the mail of the day, so mail in voting was never even considered, any more than voting online.
I would not think that that would automatically give the State the authority to suck up that bit of power. I find the court's argument weak.