A landmark law designed to keep Native American children within Native American families, has been struck down as unconstitutional by a federal judge in Texas.

US District Judge Reed O'Connor found that the Indian Child Welfare Act of 1978 illegally gives Native American families preferential treatment in adoption proceedings for Native American children based on race, in violation of the Fifth Amendment's equal protection guarantee.

On 4 October Mr O'Connor ruled that the law violated the Tenth Amendment's federalism guarantees, specifically the so-called “anti-commandeering” principle.

This was established by the Supreme Court most recently in a 2018 sports gambling case, Murphy v NCAA et al, which bars Congress from “commanding” states to modify their laws.

In this case, Mr O'Connor found that the ICWA “offends the structure of the Constitution,” since it requires state courts to implement a policy “unequivocally dictated” by the federal government.

The same doctrine has been used by at least two federal courts, in Pennsylvania and California, to block the Trump administration's crackdown on so-called “sanctuary cities”.

The ruling is a victory in the eyes of state attorneys general in Texas, Louisiana and Indiana, who argued the Indian Child Welfare Act imposed a “discriminatory framework” against non-native adoptive parents.

But in the eyes of Native American rights attorneys, the ruling is destructive, with an impact that may stretch far beyond the ICWA.

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They fear it may not only jeopardise Native American children, who are far more susceptible to being removed from their families than non-native children, data has shown.

They fear the ruling, if upheld, may also jeopardise decades of legal precedent affecting tribal sovereignty, said Dan Lewerenz and Erin Dougherty Lynch, attorneys with the Native American Rights Fund.

“The decision is jarring, and not just for its effect on ICWA, but because as far as I know this is the first time ever that a federal statute enacted to benefit Indians has been found to be unconstitutional on the grounds of equal protection, "Mr Lewerenz told The Washington Post. "It introduces perhaps an entirely new world of Indian law.

And we worry that this might be what the plaintiffs intend, that this is not just an effort to undermine ICWA, but to undermine all Indian law.”

The case at issue stems from a Texas couple's efforts to adopt a Native American baby whose biological parents are from the Cherokee and Navajo tribes.

The couple, Chad and Jennifer Brackeen, fostered the baby from the time he was 10 months old until he was 2. At that time the Brackeens sought to adopt him with the support of the baby's biological parents.

But a family court in Texas thwarted their plans, blocking the adoption on the grounds of the Indian Child Welfare Act. The family sued in October 2017, joined by the state of Texas, Louisiana and Indiana.

The couple later successfully petitioned the court for the adoption, but the lawsuit challenging ICWA continued. The Cherokee Nation and several others intervened as defendants.

The law does not bar non-Native American families from adopting or fostering Native American children outright.

But in order for a non-native family to succeed, they have to show “good cause” that the child can't or shouldn't be adopted by other Native Americans - a main hurdle for the parents in this case.

The protections were enacted for good reason, said Sarah Kastelic, executive director of the National Indian Child Welfare Association.

At the time ICWA was drafted, Native American children were being taken from their families at astonishing rates, a systemic problem that reflected a continuation of decades of assimilation efforts, ranging from land allotment to boarding schools, Ms Kastelic said.

“This was very intentional separation of native children from their families, from their culture, from their language,” Ms Kastelic said. “At the time, it was thought that this was really in the best interest of Indian children, that assimilation, that living with non-Indian, predominantly white families, was really going to be better for native kids. That was the climate at the time.”

According to survey data from the Association on American Indian Affairs contained in a 1977 Senate committee report, approximately 25 to 35 per cent of all American Indian children had been separated from their families and placed in foster homes, adoptive homes or institutions.

Roughly 85 to 90 per cent of those children in foster or adoptive homes were placed in non-Indian homes.

Senator James Abourezk, chairman of the Select Committee on Indian Affairs, said on the floor in 1977 that the federal government's lack of action on the issue had allowed state child welfare agencies to “literally steal Indian children” from their families, resulting in their way of life being “smothered.”

The Indian Child Welfare Act strengthened native parental rights and, in the event that a child had to be removed, mandated that courts consider the preferred Native American placements.

The first preferred placement is the child's extended family member, followed by another member of the child's tribe. If none of those options work, members of other Native American tribes are preferred.

The main dispute in the lawsuit boiled down to whether this preferential treatment was based on race or instead based on the child's political affiliation with the tribe as a citizen. Mr O'Connor ruled that it is a “race-based” statute - an interpretation that the federal government and tribes disputed.

Mr Lewerenz compared the adoptions of Native American children to international adoptions, stressing that race is not part of the equation in those adoptions - rather, it's the relationship between nations.

“It's important to understand that when Congress is dealing with federally recognised tribes, it is not doing so on a racial basis. It's a political relationship between the United States and the tribe,” Mr Lewerenz said.

His colleague, Erin Dougherty Lynch, added that this is true not only in the ICWA but in all laws related to Indians, such as the Major Crimes Act, which requires the federal courts rather than tribal courts to prosecute Indians who commit violent crimes.

As the federal government noted in its brief, the Supreme Court has upheld laws providing “special treatment” of Indians as long as the laws are specifically tethered to "Congress" unique obligation towards the Indians.”

The high court has in the past rejected claims that such special treatment is based on race, the government noted in its brief.

Instead, the court has agreed with the federal government that the “special treatment” is instead “rooted in the unique status of Indians as "a separate people" with their own political institutions,” as the court held in a 1977 case involving the Major Crimes Act.

But Mr O'Connor ruled that the Indian Child Welfare Act was not “narrowly tailored” enough to accomplish its purpose, a key requirement when laws are being challenged on the basis of race.

Mr O'Connor took issue with the fact that any Native American family could take precedence over a non-native family as the adoptive parents, even if the child does not belong to the same tribe.

Additionally, he objected to the fact that even children who are not officially members of a tribe, but whose biological parents are members, could still qualify for ICWA protections. He called them “potential Indian children,” a descriptor of humans that Mr Lewerenz said he had never heard of before.

“The ICWA's racial classification applies to potential children, including those who will never be members of their ancestral tribe, those who will ultimately be placed with non-tribal family members, and those who will be adopted by members of other tribes,” Mr O'Connor wrote.

“Because two of the three preferences have no connection to a child's tribal membership, this blanket classification of Indian children is not narrowly tailored to a compelling governmental interest.”

Because he found ICWA unconstitutional, Mr O'Connor also invalidated a 2016 change in regulations intended to tighten criteria about what it means when non-native parents must show “good cause” that ICWA can't be followed.

Previously, “good cause” was left open to interpretation by courts. But the 2016 rule change raised the evidentiary standard and placed the burden on the non-native parents.

It also made clear that courts couldn't compare Native Americans' socio-economic status with that of non-native people when making decisions about adoptions.

When the Bureau of Indian Affairs announced the rule change in 2016 and sought public comment, Texas did not come forward with any concerns about ICWA, according to a brief filed by the federal government.

“To the contrary, Texas Department of Family and Protective Services stated that it 'fully supports the Indian Child Welfare Act, noting that it worked collaboratively with tribes and community stakeholders to develop best practices that will inure to the benefit of tribal children and families.”

Attorney General Ken Paxton cheered Mr O'Connor's ruling in a statement on 5 October, saying it “protects the best interests of Texas children”.