Ref. No. 1701/43-1340
In the name of Allah the most Gracious the most Merciful
(1) It is permissible to use all items available in the market, whether they are labeled as halal or not. However, if there is any doubt about a particular product, or if it is known to be suspicious by any reliable source or its product code. If haram ingredients are specified thereupon, then caution is required. Halal certificate can be trusted if issued by a reliable institution, and thus its certified products can be used.
(2) Kosher slaughter, used in Jewish custom for halal slaughter. If a Jew knows how to slaughter according to the teachings of his religion, his slaughter will be halal. Therefore, because of being the People of the Book, Kosher Zabiha will be halal. However, today's People of the Book do not usually take care of their religious teachings; hence kosher slaughter should be avoided.
And Allah knows best
Darul Uloom Waqf Deoband