When have countries refused to take back land?

Matt Yglesias writes that the Jordanians don't want the West Bank back, at least not in anything resembling its current state.  The Palestinians would be regarded as destabilizing by the Jordanian government.  How many historical examples can you find of countries refusing to take back territory that was once, in some form or another, theirs?  Spain probably wouldn't take back Ecuador but the offer will not come because the Ecuadorean government values the land.  So when is the political shadow value of land negative for both governments?  (Of course it's not negative for the Palestinians.)  The West Bank aside, I can't think of examples where there is both a possible offer and a refusal to take the land back.

Could Puerto Rico be an example?  Maybe the U.S. would gladly "give it back" (that is debatable, however) but it seems that Puerto Rican voters don't want full, unencumbered title.