25 CFR §11.603

1. (a)The following marriages are prohibited:
   1. (1)A marriage entered into prior to the dissolution of an earlier marriage of one of the parties;
   2. (2)A marriage between an ancestor and a descendant, or between a brother and a sister, whether the relationship is by the half or the whole blood;
   3. (3)A marriage between an aunt and a nephew or between an uncle and a niece, whether the relationship is by the half or the whole blood, except as to marriages permitted by established tribal custom;
   4. (4)A marriage prohibited by custom and usage of the tribe.
2. (b)Children born of a prohibited marriage are legitimate.