The takeover is scheduled for Oct. 1, The New York Times reported. But tribal members and whistle-blowers in the government complain the Bureau of Indian Affairs still downplays the problem on the Spirit Lake Reservation, the newspaper said.
One out of every 163 residents, a total of 38, is a registered sex offender. Violent attacks on children are seldom prosecuted or even reported, officials say.
In May 2011, two siblings, a girl, 9, and boy, 6, were sexually assaulted and killed.
"It bothers me that it is so accepted, that it is considered so normal. It's lawless," Molly McDonald, a former tribal judge dealing with juveniles, told the Times.
Betty Jo Krenz, a former social worker for the Spirit Lake Sioux tribe, said that children abused in one generation become the abusers in the next. Observers also point to high rates of poverty and alcoholism among the reservation's 6,200 residents.
Thomas F. Sullivan, of the federal Administration for Families and Children, told the Times that he has been banned from talking to the news media.
"If we fail in our role as leaders, we will deserve the same condemnation society so correctly applied to those leaders at Penn State and in the Catholic Church who, knowing of the abuse being inflicted on children by their colleagues, did nothing, failing in their basic obligation to protect children," Sullivan said in a memo last month.