What is the ruling on selling products that contain gelatin of unknown source, and is there any doubt concerning this trade?

Gelatin extracted from an animal slaughtered according to Islamic law (dhakāh) is halal (permissible). Gelatin extracted from an impure animal, like a pig, or from an animal not slaughtered according to Islamic law, is haram (forbidden). If the origin of the gelatin is unknown, then circumstantial evidence should be considered: if the source is a non-Islamic country that does not observe Islamic slaughter, the default ruling is prohibition. However, if it is highly probable that it is from an animal slaughtered according to Islamic law, then it is permissible. If the possibilities are equal and there is no preponderant evidence, then the side of prohibition takes precedence.