An interesting counter-example is the Museum of Us in Balboa Park, San Diego. They have on display a Mexican mummy (if memory serves, naturally dessicated by a

An interesting counter-example is the Museum of Us in Balboa Park, San Diego. They have on display a Mexican mummy (if memory serves, naturally dessicated by a desert burial) that was smuggled across the border from Mexico to the US. At some point, the museum got in touch with Mexican authorities and agreed to repatriation. However, the museum they've worked with in Mexico doesn't really have use for the exhibit, so it's on indefinite loan to the Museum of Us with full understanding that this is a generous privilege provided by the museum in Mexico and the people of the nation. ... All in all, a quite excellent win-win negotiation to mutually-agreeable conclusion, it seems.