If a law is in the talmud, and not in the shulchan aruch, then is it followed, or not followed?

Question

If a law is in the talmud, and not in the shulchan aruch, then is it followed, or not followed?

Can you give any examples to show one way or the other e.g. a law in the talmud not in the shulchan aruch, and is it followed or not? I'm wondering if one can prove one way or the other e.g. if all cases of a law in the talmud and not the shulchan aruch are followed. Or if all cases of a law in the htalmud and not the shulchan aruch, are not followed.. Or if it's a mixture?

And if there's any law or rule, that deals with that situation of the applicability of a law in the talmud that is not in the shulchan aruch.

Answer 1

Many laws exist in the Talmud that don't exist in Shulchan Aruch.

The most common cases are those that don't apply nowadays, like sacrifices etc... There are other areas that I don't recall being in Shulchan Aruch like Loshon Hora, which is an example of something omitted but followed (or at least should be followed).

There are also interesting "guidelines" for speech (see first few daf of Pesachim) like to not say words like "Tumah" (there are exceptions). I believe the Chazon Ish would not say the word "Dog" (people used this deragatorily by calling others a "dog"). Instead the Chazon Ish would say "four legged one" (in Yiddish). So this guideline would be followed by those who are scrupulous. Though I don't know if it is a "law" or simply a guideline for behaving correctly.

Similarly Chagigah 5a. To not spit and disgust someone. I can't say if it's a law, but Shmuel does hold that someone would be punished for doing something like this. It is brought down in Kaf Hachaim 116:70. But I see no source for Shulchan Aruch (though there might be one I don't know).

My best guess is that the Shulchan Aruch is built around the Tur and so you'd have to go and see how the Tur decided on which areas of Halacha to include from Gemara.

Interestingly enough see an example for why something from Tur was left out of Shulchan Aruch

Answer 2

The Shulchan Aruch and the Rema had their own methodology.

As is written in the Introduction to Beit Yossef (available here), when writing the Shulchan Aruch, Rabbi Yossef Karo relied in the majority view by 3 rishonim, which are, the Rif, the Rambam and the Rosh. When all three omitted some law of the Talmud, the Beit Yossef would follow the major rishonim which did in fact write about the subject.

The Rema methodology (brought up in his book Torat Chatat, available here) was to add commentaries when the halacha from the Shulchan Aruch conflicted to practices of ashkenazi jews of his times.

Some times, the rishonim would not bring some practice from the Talmud because they sustained it was not relevant to their times for some specific reason (depends on what the case is), and if, for example, (1) other major rishonim would write explicitly that indeed the practice was not relevant for whatever reason (or simply no other rishonim would write about it) and (2) the norm practice was not to follow this practice, it would fit in the criteria not be brought up by the Shulchan Aruch (point 1) or the Rema (point 2).

An example this would be the prohibition of "linat laila" (overnight stay - consisting of eating a peeled garlic/onion/egg which was stayed overnight), brought up in the Talmud in Massechet Niddah 17a, about which the Rabenu Tam sustained is not relevant in our days, and it was omitted by the Rif, the Rambam and the Rosh (because they hold like Rabenu Tam, see Shut Iad Meir Siman 19, available here), therefore is omitted by the Shulchan Aruch and the Rema as well (see Shut Iad Meir mentioned above about the habit of the world being not be cautious about this). In this specific case, some other later authorities, like the Aruch Hashulchan in Yore Deah 116:22, the Shulchan Aruch HaRav, Rabbi Ovadia Yossef and others, hold like the disagreeing part of the discussion and hold that this prohibition is relevant still in our days. For more about the discussion on this prohibition see here