Opinion about treasures in abroad

After the trip to The British Museum, there is a debate about the treasures of China which is presented in oversea, such as in The British Museum. In my opinion, the treasures should be treated separately according to the different way of losing to abroad. If the treasures were robbed or stolen by foreign country, there should be returned to theirs original owner. On the other hand, if the treasures were given as gifts or traded obey the laws, then it is the right for the present owner to continue the collection. The most important thing I want to emphasize is that the orignal country should have the condition to collect the exhibits, because these items not only the treasure of theirs country, but also to the whole humen world.