Good point, well made. In the last 15 - 20 years UK museums entered into national and international agreements to ensure they acquired artefatcs through legitimate and traceable means. This was not always the case in the past.
So now a museum in the UK can't just get a new leopard to stuff, for the heck of it - it has a set of rules to follow. Similarly, if buying a work of art, they are duty bound especially if using public money to ensure the seller has title to it and it didn't fall off the back of a Nazi lorry.
Many countries have shown great interest in getting their cultural material back - North American and Australian groups have recently had artefacts and human remains returned to them.
Problems arise where a museum has based a huge part of its displays around a particular artefact - the Elgin Marbles is a case in point. Giving them back leaves a gaping hole - and this is where UK museums argue that the country asking for return of goods is not yet capable of caring for them.
Egypt has become very touchy in recent years about the quantity of cultural heritage kept abroad.
On the other hand, it can be argued that many of these objects were bought and paid for, fair and square.....they were the luxury souvenirs of their day and the inhabitants of their countries of origin were often only too pleased to flog them.
And some major collections still turn as blind an eye as they dare to the origins of their purchases.