A new drink was becoming very popular, and as I was unable to verify the validity of the unfamiliar hashgacha on the can, I advised my students not to drink it for now. One student did so anyway, and then felt guilty and, as part of his personal teshuvah, swore verbally that he will not drink it again. Recently it has come to light that the hashgacha is in fact considered reliable by many in the kashrus world, and when I publicized this, the student asked if he can continue drinking it, as he only swore under the assumption that it isnt kosher. What is the halacha?

ב"ה Shalom I consulted a major Posek in Eretz Yisrael, and he said that since he swore mistakenly, he has to retract on his oath. Therefore, he should do a Hatarat Nedarim in front of 3 people, in the same way it is done Erev Rosh Hashana, with him specifying the oath which was made. Once this is done he can resume drinking this drink. All the best