Which is why I've been consistent in saying that the state legislatures can choose arbitrarily, but if they hold an election for electors then the electors must

Which is why I've been consistent in saying that the state legislatures can choose arbitrarily, but if they hold an election for electors then the electors must be selected using only votes from that state. They can avoid this by choosing not to hold an election. But if there's no election, then there's no national popular vote. Thus, in either scenario, there is no possibility of a national popular vote interstate compact.