The amount of urban Indians who are enrolled or not is part of the problem and a real issue here.
Here is a case from Michigan where the mother said her children were Delaware and entitled to protections under the Indian Child Welfare Act of 1978.
Allowing time for tribes to respond is a big issue since many tribes have few or overworked enrollment officers who can't always get historical information to enroll their members and/or their children who live off rez. If tribes did manage enrollment at birth, it would certainly help.
Making more Native children adoptees is not a solution. Helping American Indian families stay together is federal law!