Complex sentence: Later that year, the Bureau of Indian Affairs held that the exclusion of Black Seminoles constituted a violation of the Seminole Nation's 1866 treaty with the United States, as the treaty was made with a tribe that included black as well as white and brown members.
Split into simpler sentences: Later that year, the Bureau of Indian Affairs held that the exclusion of Black Seminoles constituted a violation of the Seminole Nation's 1866 treaty with the United States. They noted that the treaty was made with a tribe that included black as well as white and brown members.