How do you get custody if you are a father not married On the birth certificate but your son is out of state on a native American reservation?

If your son is Native American it will be close to impossible to get him away from the reservation due to the Indian Child Welfare Act (ICWA). If his mother is a fit parent they would not take him away from her. if you move to his state you can get shared custody and visitation. To get your parental rights you have to prove paternity with a DNA test and then you can petition the court for custody, visitation and pay child support. But consult a lawyer on this.