Chullin 41 - A Person Cannot Forbid Something That Is Not His
If an idolater performed a libation with a Jew's wine, but did it not in front of an idol, then Rabbi Yehudah ben Beteira and Rabbi Yehudah ben Bava say that the wine remains kosher, for two reasons: libations are normally done in front of an idol, and moreover, a person cannot forbid something that is not his. This point of view argues against what Rav Huna said about slaughter in front of idol .
This opinion also argues against the concept of kosher wine. According to it, if a Jew owns the wine, it never becomes non-kosher, even if touched or processed by non-Jews. However, it does not become law, and it was not mentioned in the whole tractate of Avodah Zarah .
One may not slaughter into a sea or into a river, because it may seem that he is slaughtering to the spirit of the sea or the river. One may slaughter into a pool of water, because blood mixed with water would never be used in idol worship.
If one slaughters a regular animal in the name of some free-will offering, then people may confuse it with an actual offering, and the shechitah is declared non-kosher.
Art: Carl Spitzweg - Still Life With A Jellyjar, A Carafe And A Bottle Of Wine