Is all wine kosher?

...there are no "truth in labeling" laws requiring a winery to label its products or to divulge anything in writing or by telephone about the ingredients or process it uses. The Bureau of Alcohol, Tobacco, and Firearms has a list of substances permitted for use as fining agents, and one must assume that the Government's list includes precisely those substances for which wine makers have sought approval. That list includes casein, caseinates, lactose, monostearates, gelatin, isinglass (a fish glue often made from sturgeon bladders), and non-fat dry milk powder. Although there is a negligible residue of the fining agents left in the wine after they trap the particles suspended in the wine and settle down to the bottom, if we accept the principle of ein mevatlin issur lechatchila (there is no prior nullification of a forbidden substance), the fact that there is a residue at all raises questions. Specifically, must we not assume that without someone actually standing on the site watching the ingredients which are added to the wines, the wines are, at best, dairy and, at worst, unkosher?

There is a principle in Jewish law such that a substance is legally nullified if it constitutes one sixtieth or less of the volume of the mixture into which it falls, but that principle applies only retroactively, i.e., if the substance was added accidentally...The principle of no prior nullification (ein mevatlin issur lechatchile), however, has certain exceptions. According to many authorities, one exception is those situations in which the person adding the forbidden substance does so not to nullify it but rather for some other reason (beshe'eino mitcaven). So, for example, if worms fall into honey, you may heat the mixture until it melts and then strain it because your intention is not to nullify the taste of the worms in the honey but rather to fix the honey.

Ezekiel ben Judah Landau (the Noda B'Yehudah, 1713-1793) ruled permissively in the very case before us. (YD 26) The way he phrases the question indicates that fining wine with an unkosher fish had been done by the Jews of Poland for twenty years and had become common practice among the Jews of Germany too by the time he wrote his responsum.
(The question revolves around) Krok, which some call Heusen Bleusen, which is the bladder of the fish called Heusen, which is an unkosher (tamei) fish. People dry the bladder of that fish and insert it into the drink which is called med in Poland, or honey juice. Its nature is to precipitate the lees and to clarify the drink. In Germany they are already used to acting like this, i.e., to put it into barrels of wine for this reason, and it is now about twenty years that they began doing this also in Poland in the drink of honey juice called med. And the great scholars of the generation were aroused by this to forbid it on the grounds that it remains in the drink, and "that which is preserved is treated legally as if it were cooked" (i.e., it is as if the juice and the unkosher fish were cooked together). And if one argues that it (the unkosher fish) is nullified by being less than one part in sixty, we do not nullify a forbidden substance ab initio. And there are those who want to permit the practice on the grounds that it is dried out, and it is therefore like wood which has no taste whatsoever, and they see it as being analogous to the inner lining of a stomach. And there are those who want to permit the practice on the grounds that we only restrict prior nullification when it is one's intention to nullify, but here the intention is only to clarify the wine and not to give it a taste. My honored cousin, the rabbi, the great luminary, Rabbi Joseph, the head of the court and the academy of the city Hadesh in the region Cracow, ruled to forbid the practice. But since the custom has already spread to permit the practice in the regions of Germany and Poland, I have decided to write according to my humble opinion...
For all the reasons mentioned above, it seems that it is permitted to put Heusen Bleusen into the wine or the drink which they call med in Poland because the intention is not to nullify but only to clarify the drink and to precipitate the lees. And "it is good for Israel, for if they are not prophets, they are children of prophets." (Pesal;im 66a) According to my humble opinion it is completely permissible.

The original motivation for the prohibition against using wine made or touched by non-Jews was to prevent mixed marriages- "because of their daughters," as the Talmud phrases it. If anything, that problem is more acute in our day than it was in Talmudic times.
If I thought for one minute that prohibiting wine made by Gentiles would have the slightest effect on diminishing the number of mixed marriages, I would drop all other concerns and opt for prohibiting it on that basis alone. I frankly doubt, however, that prohibiting wine touched by non-Jews will have any effect whatsoever on eliminating or even mitigating that problem. Other spirits prepared by non-Jews were permitted long ago, and it is precisely at the cocktail party where most initial socializing takes place. Moreover, the real factors creating our high rate of intermarriage have little, if anything, to do with the laws of kashrut in general, let alone the kashrut of wine in particular. Few of those who plan to intermarry keep kosher at all, and those who do will not be prevented from marrying their intended spouses by a prohibition against drinking wine with them.
Moreover, as Rabbi Silverman points out, the prohibitions originally instituted against the bread, oil, and cooked foods prepared by non-Jews have been abrogated long ago. If one were keeping these strict measures in order to prevent social intercourse between Jews and Gentiles, then the policy would at least be consistent. Such a policy would be ineffective, however, because Jews in their modern business and social contacts will not, and often cannot, observe such rules. We have enough difficulty convincing them to observe the laws of kashrut! Even if a return to all of the former prohibitions could be effectuated, it would not be desirable. In keeping with our acceptance of the conditions of modernity, we in the Conservative movement would undoubtedly hold that, short of mixed marriage, Jews should have social and business contact with non-Jews