The Court decides what the Constitution means. By definition, they can't rule outside of it.
As far as overruled decisions go, they weren't wrong when they were made; the scope of the Constitution changed.
You might not like that argument, but it's true. By definition, the Supreme Court decides what the Constitution means. Incidentally, why does the Court have the power of judical review? Because it says it does--you can't find the power of judicial review in the Constitution; it's not there. They have power because they say they do. If you want a more compelling case for infallibility, look no further.
George Orwell, is that you??
O.K., with this statement, I am begining to suspect you are being sarcastic. I hope this is the case.