Land is land. People are people. Nation states are neither. Just because gemstones were mined in a geographic area doesn't mean that they morally belong to whoever currently resides/rules in that area.
Once the *people* involved in a specific historical event are long gone it's tenuous to imply that the descendants of those parties have a moral obligation to each other. Inheritance is going to be inequitable regardless--it's questionable to assume that anyone deserves to inherit even justly acquired property. So trying to unravel history and decide who deserves what inheritance is ridiculous, even more so when nation states are involved.
Once the *people* involved in a specific historical event are long gone it's tenuous to imply that the descendants of those parties have a moral obligation to each other. Inheritance is going to be inequitable regardless--it's questionable to assume that anyone deserves to inherit even justly acquired property. So trying to unravel history and decide who deserves what inheritance is ridiculous, even more so when nation states are involved.
We have statutes of limitations for good reasons.