@oralloy,
Leaving it to "state legislatures alone" doesn't really violate states' rights.
Sure it does. That's why the SCOTUS is around. Like when States send the wrong people to death row. Or apportion districts in an overt attempt to deprive classes of people the right to vote.
SCOTUS has ruled over and over that while the State legislatures have the duty to apportion, they do not have the right gerrymand in the face of denying Constitutional rights to citizens.