I was thinking about Rav Shach's answer in Avoda Zara 23 side b and now I think it is right. The reason I say this is that even when the land of Canaan was given to Avraham, who says he wanted to get ownership of the asherot [trees that had been planted to be worshipped.] And just for argument's sake let's say he got ownership of them anyway. Then what would be the new idea? We already know that an idol that belongs to a Israeli needs to be burned. So this Gemara wants to tell us something new, I.e. that for an object to become forbidden as an idol, it does not need to be owned by the person worshipping it. Rather it is enough that the owner does not object. And in fact this is the source of that law.
_______________________________________________________________________
I was thinking about רב שך answer in עבודה זרה כ''ג ע''ב and now I think it is right. The reason I say this is that even when the land of Canaan was given to Avraham, who says he wanted to get ownership of the אשות [trees that had been planted to be worshipped.] And just for argument's sake let's say he got ownership of them anyway. Then what would be the new idea? We already know that an idol that belongs to a Israeli needs to be burned. So this גמרא wants to tell us something new, I.e. that for an object to become forbidden as an idol, it does not need to be owned by the person worshipping it. Rather it is enough that the owner does not object. And in fact this is the source of that law.
__________________________________________________________
