Norman Williams makes an interesting argument - but I don’t think it would actually hold up.
Article II, Section 1 certainly does give the state legislatures the right to appoint electors in whatever manner they want to do so.
“Each State shall appoint, in such Manner as the Legislature thereof may direct”
His argument against this relies, in part, on the decision made in the “U.S. Term Limits, Inc. v. Thornton” case in 1995. It decided that the states could not impose term limits on their members of Congress.
The argument in favor of allowing the states to imply these limits came from Article I, Section 4, specifically the part that states that the states may set the “Times, Places and Manner” of holding elections for Congress.
The (successful) argument against was that this imposed a new qualification requirement on members of Congress beyond those specified in the Constitution. And since this encroached on Federal authority, it should not be allowed.
Another part of the argument comes from Article I, Section 10, which reads “No State shall, without the Consent of Congress ... enter into any Agreement or Compact with another State”. However, in “Virginia vs Tennessee” (1893) it was decided that this only applied in cases where the compact between the states eroded the powers of the Federal government.
The approach neither places additional qualifications on elected officials, nor does it erode the powers of the Federal government.
Not being a constitutional scholar nor a SCOTUS scholar, I can't argue the merits of the ruling.
However, I can offer the lay observation that this clause might have been intended to keep states from ganging up on each other, rather than erode federal power (that's a rather insular view coming from a federal branch, BTW).
For instance, what is to prevent all the coal-producing states from forming a compact amongst themselves to deny coal to the rest of the union? There is no "federal power" involved, but a compact like this would surely hurt the nation.
What if coastal states compacted to deny fish to the heartland states, or heartland states compacted to deny wheat to the coastal states?
Wouldn't Congress want to step in and stop these practices from happening
-PJ