What are the ways in which tribal governments have acquired real property?

According to Felix S. Cohen’s Handbook of Federal Indian Law, 1982 Edition, there are six ways in which Indian tribes have acquired interests in real property:

• by action of a prior government;
• by aboriginal possession and excise of sovereignty;
• by treaty;
• by Act of Congress;  
• by executive action (reservations set aside by Executive Order); or
• by purchase.