The today’s Christians have forsaken the slaughtering way prescribed in their religion and they are not acting upon their religious commandments, so they are not abiding by their religion; therefore their slaughtered animals will not be allowed for Muslims until it is known about a particular meat that it was slaughtered in prescribed manner. So, the meat available in Christian market will not be halal. But, the meat available in Muslims areas (whose slaughterer is not known) will be considered as Sharai and halal until it is known that is was slaughtered in non-Islamic way.
The meat imported from non-Muslim countries is not allowed to consume, even if the packet clearly says: ?slaughtered in Islamic way?; since it is proved that such confirmations are not reliable. Therefore, its consumption will not be allowed until it is known about a particular meat that it was slaughtered Islamically. (Fiqhi Maqalat, 4th volume)
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband