

NPV would be insulated from SCOTUS bullshit by an explicit authorizing act. USC 1 § 10:
No State shall, without the Consent of Congress, … enter into any Agreement or Compact with another State, …
There is some precedent suggesting that a compact which decreases the power of the states wouldn’t need it, but precedent also said abortion was a right, the 14th amendment was self-executing, and POTUS could forgive debts.

And interestingly, the NPVC apparently has text specifying how a state could withdraw.
https://www.nationalpopularvote.com/bill-text