Is it illegal to retain the corpse of a loved one?

Yep, it is illegal. The body does not become property of the State however there are laws and regulations regarding the proper disposal methods of a body, the public health steps that are required and the manner in which a body is to be treated. To keep it at home, in a freezer or sitting in a chair in the den watching his/her favourite TV shows is considered to be offering indignities to a body and to bury it in the back garden is improper disposal.