US states file brief in support of disenfranchising PA, WI, MI, GA [pdf]
supremecourt.gov
supremecourt.gov
The claim appears to hinge on:
"Democratic accountability in the method of selecting the President of the United States is a powerful bulwark safeguarding individual liberty. By identifying the “Legislature thereof” in each State as the regulator of elections for federal officers, the Electors Clause of Article II, § 1 prohibits the very arrogation of power over Presidential elections by non-legislative officials that the Defendant States perpetrated in this case. By violating the Constitution’s separation of powers, these nonlegislative actors undermined the liberty of all Americans, including the voters in amici States."