"excluding Indians not taxed"

     The phrase "excluding Indians not taxed" occurs several times in the  Constitution of the United States. This does not mean that Indians don't pay taxes. American Indians, also called Native Americans, were considered citizens of their Indian nations or tribes, and not of the United States. They were not counted in any census which was used to levy taxes according to population. Indians were also not counted in any census used to apportion representatives in Congress.
    American Indians couldn't vote in elections until they became citizens of the United States in 1924.  The last states to keep Indians from voting held out until 1948, claiming that Indians didn't pay local real estate taxes on tribal or reservation land. The Indians didn't attend the local schools or use any other local services, since their relationship was with the federal government and the Bureau of Indian Affairs.
      You can read in the 14th Amendment to the Constitution that "all persons born or naturalized in the United States and subject to the jurisdiction thereof , are citizens of the United States and of the State wherein they reside".
     Indians didn't live in any "state", since reservations were considered federal territory, even within a state.  The relationship of the Indians to the federal government was by treaty, so it could have been argued that the Indians were not subject to the jurisdiction of the government. Since they were forbidden to leave the reservation, their laws were made and enforced there. Some of the reservation restrictions were still in force in the 1970's.