Last night Michael, Ben, and I spoke with Robert Hardaway of the DU Law School to talk about the Colorado legislature's misguided attempt to amend the Constitution without, you know, actually amending the Constitution. I've posted before (and Twittered relentlessly) about the attempt to join an interstate compact to render the Electoral College a dead letter.
He agreed that the Supreme Court was exceedingly unlikely to permit such a compact under Article I Section 10:
No State shall, without the Consent of Congress, lay any Duty of
Tonnage, keep Troops, or Ships of War in time of Peace, enter into any
Agreement or Compact with another State, or with a foreign Power, or
engage in War, unless actually invaded, or in such imminent Danger as
will not admit of delay. (yes, emphasis added - ed.)
He also pointed out that there's no definition provided of the "National Popular Vote." Apparently in 1960, the newspapers added up the popular vote and decided Kennedy won, while Congressional Quarterly came to the conclusion that Nixon had won the popular vote. The determination of what count to use would rest in the hands of the state's top election official, presumably - but not named as - the Secretary of State.
One point we didn't get around to discussing was the question of Puerto Rico. Puerto Rico is, of course, not a state, but its citizens are US Citizens. Would they suddenly be eligible to hold a Commonwealth-wide referendum and have their votes counted? At this point, I certainly wouldn't rule out the State Supreme Court ruling that way.