Questions about homesteading on an Indian Reservation

Hello. I am working to look into a question about a piece of property and have been stuck, and was wondering if you might be able to point me in a direction to try?

This piece of land is located on an Indian reservation (Port Madison Reservation) in Washington State. The relevant treaty was signed with the US government in 1855, and the reservation formed in 1864. However, the land patent (a homestead certificate) for this land was signed from the US government "to settlers on the public domain" in 1890. My question is, how was the US government able to give this land as a homestead to this settler since it was owned by the Suquamish tribe and was on their reservation? It would seem that it would need to have been a bill of sale of some variety from the relevant Suquamish family to the settler. Is this an indication that the US government sold the land without the tribe's consent? Or that they used the noncompetence laws to force the sale, even though the tribal family didn't want to?

I would appreciate any help with directions to head in for researching this, or any insights. Thank you!