William Baude and Michael McConnell in The Atlantic:

In a constitutional republic like ours, legislatures ultimately derive their authority from the people. This authority is conveyed through written constitutions that charter the government, vest power in different branches, and regulate the exercise of that power. A state legislature’s power to pass laws should be seen through this constitutional lens. Because state legislatures derive their lawmaking power from their own people, their authority is limited to what their state constitution gives them. When the federal Constitution gave state legislatures additional authority, it took them as it found them, as created by state constitutions rather than a new free-floating entity. State legislatures are not independent of their constitutions.

But the claim that state courts may hold state legislatures to state constitutional limits does not mean that they can replace the legislature. The federal Constitution’s text explicitly empowers one of these branches to regulate federal elections, not the other. (There is one Supreme Court case from 2015 that adopted a very capacious definition of legislature to uphold an independent redistricting commission, but that decision was 5–4, distinguishable, and, most important, wrong.) State legislatures must act according to their state’s constitutional constraints. But it must still be the state legislatures that act.

What does this principle mean for concrete cases?

It means that state constitutional provisions can restrain legislative districting, such as by limiting the use of partisan gerrymandering. The broad challenge to state constitutional law in Moore therefore should fail. But it also means that the North Carolina courts do not have independent constitutional power to adopt their own map.