Those who aren't of the Twelver Shia sect, whether they are of the Shia sect, such Zaydis and Ismailis, or of the Sunni sect, are all considered Muslims and pak, making the food they cook and the meat they might sell halal and pak. Imam Khomeini says: “One of the conditions of the person slaughtering the animal is that he be Muslim or at least share the ruling of a Muslim, like the child of a Muslim. Therefore, meat that comes from an animal slaughtered by a non-Muslim, let him be mushrik or non-mushrik or even of the People of the Book, will not be halal, according to the stronger viewpoint on the issue. As a result, iman (being a twelver Shia) isn't a condition [for the meat being halal]. So the meat of animals slaughtered by all Muslim sects is halal, except for the Nasebis, even if they proclaim that they are Muslim.” Now, if the Aghakhanis are considered a Shia sect, their meat is halal, subsequently, any food they might cook is also halal and pak, and they can be trusted.
 Imam Khomeini, Tahrirul-Wasilah, vol. 2, pg.146.
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