The permissibility of eating rennet-made cheese
The ingredients that go into some European types of cheeses include rennet. Rennet is derived from the stomach of calves and used in the making of cheese. I would like to know whether it is permissible for Muslims to eat these cheeses since the calves are not slaughtered according to Islamic precepts.
Once the Prophet (peace and blessings be upon him) passed by a house and found a dead sheep near it. He suggested to its inhabitants that they should take the hide of that sheep and make use of it. They told him that the sheep had died of natural causes and as such was carrion. It is known that carrion is forbidden to eat. The Prophet (peace and blessings be upon him) told them that he did not mean that they could eat it and its death from natural causes does not preclude benefitting from its hide. This applies to other parts of any dead animal. As long as we are not using it for food, then we can make use of it.
Rennet is used in the making of cheese. When used, it becomes part of a chemical process that changes its substance. Moreover, once the cheese is made, it is not possible to separate the milk and other ingredients that went into its making. It is a rule in such situations that if a substance is used in a chemical process that transforms its nature altogether, it becomes permissible to consume. This means that there is nothing wrong in eating the cheese you mention as long as the rennet is not derived from pigs, but from calves or other animals which are lawful for a Muslim to eat.
Moreover, although Europeans do not slaughter their animals in the manner prescribed by Islamic law, the meat of their animals is permissible to eat because God Almighty says that the food of people who follow the heavenly revealed religions is permissible for Muslims to eat. He did not set any conditions on the method of slaughter of their meat. What they accept as lawful in their religion is permissible for us to eat unless it is specifically forbidden in our religion, such as pork.
And God Almighty knows best.