I have a number of investments in various stocks that trade on the market. Recently, a friend mentioned that there might be a problem to own shares in a corporation that trades in non-kosher foodstuffs. Is there a halachic restriction on owning shares in such corporations (e.g. McDonalds)?
Concerning the actual sale of non-kosher products, we find in the Shulchan Aruch (YD 117:1) that one may not sell non-kosher food items on a regular basis. Most authorities maintain that although the Torah permits one to sell non-kosher meat to Gentiles (Devarim 14:21), a rabbinic decree limited this permit to sales on an occasional basis. According to others, regular sale of non-kosher items transgresses a Torah proscription (see Taz and other commentaries, YD loc. cit., based on Tosafos, Pesachim 23a).
For instance, it is permitted for Jewish slaughterhouses to sell the meat of animals that are found to be unfit for Jewish consumption. Since these sales are not part of the slaughterhouses’ ongoing business operations, they are permissible (see Shach, YD loc. cit.). Likewise, an individual who receives an inheritance of non-kosher products is permitted to sell it on to non-Jews. However, it would be prohibited to sell non-kosher foods as regular merchandise in a shop. Even on an occasional basis, it is forbidden to intentionally trade in such goods.
Two reasons are suggested by Shach for the rabbinic enactment concerning the sale of non-kosher foods. One reason, as cited by most authorities, is for fear that the Jewish trader might come to consume the foods. Shach, however, expresses some discomfort with this reasoning: Why should all Jews be considered suspect of such grave transgressions? He therefore suggests that the reason might be due to maris ayin—because onlookers might [mistakenly] think that the merchant was also consuming his non-kosher foods.
According to both lines of reasoning, there would be room to suggest that the decree does not apply to instances in which the Jewish trader does not come into direct contact with the food: There would be no suspicion of his eating the food, neither on the part of Chazal nor by onlookers. Yet, poskim concur that one may not be lenient even in partnerships with non-Jewish traders. Although there may be no practical concern of the Jewish partner partaking from the food, the rabbis made a blanket enactment, thereby including financial partnerships in the proscription (see Gilyon Maharshah, loc. cit.)