Part of my approach to how I would modify the Shulchan Aruch would be to notice the argument between the Rambam and the Raavad about rabbinical laws.
The Rambam holds rabbinical decrees do not lose their force when the reason for them drops off. The Raavad disagrees with this, and Tosphot also disagrees with the Raavad. (Any place in Shas where this issue comes up, Tosphot says this.)
So decrees of the Sages are highly connected to the reason they were made. That would mean that some laws of Shulchan Aruch would automatically change if the circumstances changed.
[When I say Shulchan Aruch I mean the four volume book by Joseph Karo written in Safed about 500 years ago, along with his commentaries-the Shach, Taz, Magen Avraham, etc. It is a very large book and to go through it takes a lot of time.
As for the contention of Supreme Court Justice Scalia, I think he is right. Laws don't change meaning over time. But he is referring to the laws of the Constitution of the USA. And that has a different ground of validity.
The ground of the Constitution is Natural Law and the contract theory of John Locke.
The Supreme Court justices are thinking in different terms than people involved with Torah think.
They might be considering the fact that if they people pass laws that are bad for them "Who are we to disagree?" I don't know if there is a name for this but it could be called "judicial minimalism."
They might be thinking if the people don't like the laws passed by the Congress and signed by the president it is their prerogative to get themselves a different Congress and a different president.
They get this chance every four years. And perhaps now would be the time to start preparing. After all more than 50% of Americans believe in conservative values. Why should it be so hard to get a president who respects those values?