Any experienced airline passenger (or reader of this blog) knows that airlines refuse to be liable for "valuables" lost or damaged in checked luggage. It's in their contracts of miscarriage and on their web sites. However, according to the US DOT, those rules do not apply to international travel between the US and foreign destinations, by treaty, according to an article in Travel Weekly magazine. The treaty in question is the Montreal Convention, as revised in 1999 under the auspices of the International Civil Aviation Organization.
As the article points out, even if an airline prohibits passengers from packing certain items in their checked baggage, once an airline accepts it, whatever is in it is protected. Of course, making an international airline, or any airline, cough up the cash when they lose or damage your luggage or its contents is another matter.