The auction catalogue correctly called the articles katsinam, but these are commonly although incorrectly called "masks."

NAGPRA, the law passed by Congress in the United States, applies to items regardless of age. Moreover, the method of obtaining ownership is immaterial; possession is not 9/10 of the law with regard to these items.
The regulations have exclusions and provide for legal contest.

Going back to an earlier post by Sugarfoot Jack, if a prehistoric pot (etc.) is taken from Federal lands or Reserves, that is illegal and subject to proseccution. If the pot is taken from private lands, it may be kept or sold, unless the item is claimed as part of "cultural patrimony," funerary or ceremonial value. In this case, the object(s) may be subject to legal decision as to whether NAGPRA applies. There have been a number of court cases.

The sale of items held abroad is legal under the laws of the country concerned; U. S. regulations, of course, do not apply.

Another legal consideration in the U.S. is the sale of items with feathers or parts of protected animals; this could also apply unless it could be proven that the feathers, etc., are not of recent origin (I am fuzzy on these regulations; they can be found easily through google).