Religious legislation is similar to the secular model: declarative principles – constitution – laws – executive orders – instructions. In Judaism, love for God and negative reciprocity to neighbors are the declarative principles. Love for God establishes the acceptance of axiomatic commandments; negative reciprocity (“do not do unto another what is hateful to you”) is the governing rule of communal life.
The Ten Commandments are the Jewish Constitution. They develop the two declarative principles. Love for God is clarified in practical terms as abrogation of other worship and divine images and reserving a weekly spot, Shabbat, for contemplation. The rejection of harming neighbors is likewise clarified: they should not be murdered or robbed, falsely testified against, and should not become objects of jealousy. One’s obligations to aliens are more limited: they should not be murdered or robbed; that’s about the maximum that normal human beings could practically accord to aliens. Obligations to parents – the closest neighbors – are more extensive: they should be respected.
Torah is a compendium of Jewish laws. They are based on the Constitution (the Ten Commandments) and, like all laws, could be theoretically changed, but contenders must overcome a huge burden of proof that the laws are either obsolete or (God forbid) initially erroneous. Torah represents eternal truth unless in particular instances definitely proven otherwise. For example, the laws against zoophilia, incest, and homosexuality develop the constitutional commandment which prohibits adultery.
Talmudic rules could be likened to executive orders. They make the laws actionable. While largely correct, Mishna and especially Gemara are open to change with the current situation in mind. Talmudic sages adapted the laws of Judaism to their circumstances; for example, they over-regulated due process and made capital punishment practically impossible because, living in the Diaspora, they could not enforce death sentences, anyway. Modern Jews are entitled to similar re-evaluation. Cavalier rejection of the Talmudic wisdom is wrong. It took five centuries to lay down the Talmud, and re-evaluation would also take time.
Finally, there is Shulhan Aruch (rather, Bet Yosef) and similar codes of detailed admonitions on everyday life, essentially a set of bureaucratic instructions with deliberately archaic leanings. Some views of Rabbi Karo were doubtful from the beginning; e.g., he rejected the traditional view supported by Maimonides that rabbis must work for living rather than rely on public funds. Much of Shulhan Aruch, e.g., its legal and commercial sections, is reasonable today and lays foundation for practically ethical society. Some rules, notably of food processing and domestic affairs, are hopelessly outdated. The contemporary rabbis criticized R.Karo for relying almost exclusively on ancient authorities rather than considering current opinions and circumstances. The Reform Movement rejects the detailed instructions altogether, and the Conservatives relegate the decision-making to local, often barely educated rabbis. Both approaches are wrong: every society needs standardized instructions on observing the laws. Jews need a replacement for Shulhan Aruch.
Jewish religious bureaucrats, as their secular colleagues, developed a huge body of unsystematic modern legal opinion. Rabbis sought to leave a trace in history and competed in inventing rules for insignificant situations such as opening a fridge on Shabbat (the action turns on the fridge’s light and increases the likelihood of starting the compressor; both prohibited on Shabbat). Jews would do well to disregard that heap of rules and deal with the situations on ad hoc basis as they see fit.