Hi ynot,
My response is in regard to the difference between “taking what is not given” and stealing and also instances where a person picks a fruit or picks something valuable from the street.
With regard to ownership of objects there are absolute / ultimate (paramaththa) rules as well as conventional (sammatha) norms. The law of the land will fall under these conventional norms / rules.
Let’s take an example where person A loses an object and drops it on the road. In the ultimate sense after A drops that object, he loses ownership of it and no one owns that object. If B walks by and picks it up and keeps it for himself he has not stolen anything, as the object didn’t belong to A, or anyone else. This is in the ultimate sense. However, in the conventional sense and even with laws of the land B may have stolen that object from A, as A still may have ownership over it.
In a similar way, if B steals something from A, say by grabbing his bag and running off, in the ultimate sense the ownership of that bag changes from A to B after the point that B takes hold of the bag. There was an instance where a man stole a monks bowl and when the monk tried to forcefully take it back from the man, the monk was told that the bowl now belongs to the man and it he shouldn’t take it back from him.
So in the ultimate sense, there can be a difference between “taking what is not given” and “stealing”.
Of course as Lal mentioned the intention plays a vital part in this process as well.