Native American collectibles range from arrowheads to pottery to jewelry and it freely passes from sellers to buyers across the globe. There are though certain items that are illegal to sell or buy. Those items directly relate to individuals retrieving items from ANY federal land.
This includes national forest, parks or any BLM land. The only exception is those that have applied for and received a permit to do so. And remember, someone who has a permit can also provide proper paperwork.
In 1990, the Native American Graves Protection and Repatriation Act, Federal law, was instituted. This not only provided a way to repatriate items back to the Native American tribes, it also prohibited the ownership of certain cultural items.
These items include human remains, funeral objects, sacred objects, and objects of cultural ritual. Some items such as burial pots and textiles are often sought after. These items are illegal for anyone that is not Native American to own.
Beware of items that appear to have been buried and obtain documentation from the seller. In other words, cover your backside. For antique Native American artifacts, the rule of thumb should be...No paperwork - No sale.
Remember though that there is a wide range of newer and legal items to be had. Pottery and rugs, jewelry and bead work, carvings and leather work, all beautiful with a deep history of the Native American people.