Is National Popular Vote Interstate Compact Constitutional for electing POTUS?

[Slander and/or Libel]

I don't think it's implicitly a compact. There are provisions of the law that passively cause it to come into effect when enough other states have passed similar measures, but there aren't any actual agreements between state governments.

[Slander and/or Libel]

Yeah, actually, I'd forgotten about the lock-in date. That's potentially troubling, though how would that be remedied? Who would have standing to take it to court in what circumstance?