Praise be to Allah.
The scholars of Islam are unanimously agreed that meat slaughtered by mushrikeen, those who worship idols and deny other religions, and all other kinds of kaafirs who are not Jews, Christians or Magians, is haraam. And they are unanimously agreed that meat slaughtered by the People of the Book, Jews and Christians, is permissible. They differed concerning meat slaughtered by Magians, who are fire worshippers. Therefore the four Imams and the majority of scholars are of the view that it is haraam, because they classify the Magians with idol worshippers and other types of kaafirs, other than the People of the Book. Some of the scholars are of the view that meat slaughtered by them (Magians) is permissible because they classify them with the People of the Book, but this is a very weak view; in fact it is invalid. The correct view is that of the majority of scholars, which is that meat slaughtered by the Magians is like meat slaughtered by any other mushrikeen, because they are like them in everything except the jizyah. Rather the Magians were likened to the People of the Book only with regard to taking jizyah from them. The evidence for that is the verse in which Allah says in His Holy Book (interpretation of the meaning):
“Made lawful to you this day are At‑Tayyibaat [all kinds of Halaal (lawful) foods, which Allaah has made lawful (meat of slaughtered eatable animals, milk products, fats, vegetables and fruits)]. The food (slaughtered cattle, eatable animals) of the people of the Scripture (Jews and Christians) is lawful to you and yours is lawful to them”
So Allah clearly stated that the food of the People of the Book is permissible for us, and their food means meat slaughtered by them, as stated by Ibn ‘Abbaas and other scholars. So what is implied by this verse is that the food of kaafirs other than the People of the Book is haraam for us. This is the view of all scholars except what is known of the odd and weak difference concerning meat slaughtered by the Magians.
Once this is understood, the meat that is sold in stores in non-Muslim countries, if it is known that it was slaughtered by People of the Book, then it is permissible for Muslims, provided it is not known to have been slaughtered in a manner different from that which is prescribed in sharee’ah. So the basic principle is that it is permissible according to the text of the Qur'aan, and we should not turn away from that except if something is proven which implies that it is haraam.
But if the meat is slaughtered by any other kaafirs, then it is haraam for the Muslims and it is not permissible for them to eat it, according to the text and according to scholarly consensus, and it is not sufficient to mention the name of Allah over it when washing it or eating it.
With regard to what some quote to prove their point, that report was narrated concerning some Muslim people who were new in Islam, and some of the Sahaabah (may Allah be pleased with them) asked the Prophet (blessings and peace of Allah be upon him) about that. They said: O Messenger of Allah, some people who are new in Islam bring meat to us, and we do not know whether they mentioned the name of Allah over it or not. This was narrated by al-Bukhaari from the hadeeth of ‘Aa’ishah (may Allah be pleased with her). Thus it is clear that there is no proof for the one who buys meat that comes to the stores and is slaughtered by kaafirs other than the People of the Book and says the name of Allah over it, because the hadeeth narrated from ‘Aa’ishah speaks about Muslims, not kaafirs. So there is no proof, because the Muslim is to be regarded as sound and righteous so long as nothing is known from him to the contrary. It may be that the Prophet (blessings and peace of Allah be upon him) told those who asked him to say the name of Allah when eating the meat so as to be on the safe side and in order to counter the whispers of the Shaytaan, not because that would make halaal the meat slaughtered by them which was haraam. And Allah knows best.
But if the Muslim is in those non-Muslim countries and it is difficult for him to obtain meat that is slaughtered in the proper shar’i manner, and he is fed up of eating chicken and the like, this does not justify him eating haraam meat and it does not mean he comes under the heading of one who is compelled or forced, according to the consensus of the Muslims. It is essential to pay attention to this matter and warn against carelessness for which there is no reason. This is what seems to me to be the case with regard to this matter which has become widespread. I ask Allah to help the Muslims to do that which is in their best religious and worldly interests and to instil fear of Him and respect for His sacred limits in their hearts and to help them avoid that which goes against His laws.