On February 12, 2008 the Hispanic Society of America filed a
suit against the American Numismatic Society over control of a
collection of some 37,000 Spanish coins formed by Archer Huntington,
who was a major benefactor of both the Hispanic Society and ANS.
It was Huntington's largesse that enabled the construction of
Audubon Terrance at 155th and Broadway in New York, where the
two societies resided for decades until the ANS's recent move
to lower Manhattan.

I can see why they'd be mad.

The speculation is that the Hispanic Society wants some cash from selling the collection and is not interested in keeping it in tact.
Legally it will be hard to sort out because permanent loan is in some ways an oxymoron.