To be fair, Sotomayor did not say AA is required by constitution, which is clearly ridiculous. Her point was that MI should change their AA policy in other methods. They should not change it by ballot measure to pass an amendment, because it would be very hard for racial minorities to pass pass an amendment to support AA. This is probably equally or even more ridiculous. I respect Ginsburg as a jurist, and was disappointed the signed on such a ridiculous opinion.
I admit that was an oversimplification, but I read the text of Michigan Proposal 2. I don't see anything offensive in that amendment that violates the United State Constitution. To strike it down would be to say that the text somehow violates some right of affirmative action. I don't see how you can see otherwise. This isn't singling out a specific class from protections or discrimination as Romer v. Evans ruled against.
Her argument was that affirmative action is a policy to reduce racial discrimination and must therefore be treated as a special thing. So by putting a ban on affirmative action in the constitution rather than merely statute you were making it harder to obtain the special thing. And the government is only supposed to make it easier to obtain special things, not harder. By her argument you could substitute affirmative action with literally any policy claimed to be about racial discrimination and she'd reach the same conclusion.
