The Supreme Court debated on Wednesday a 1978 law that prioritizes Native American families for custody of Native children, as a response to a decades-long effort to assimilate those children by removing them from their tribes.

The plaintiffs, who include non-Native families seeking to adopt Native American children, claim that the law violates the 14th Amendment by favoring one race over others. Proponents of the law argue that its preferences are based on the fact that Native American tribes are sovereign entities, rather than race.

Several members of the court’s conservative wing indicated during more than three hours of oral argument that they were inclined to view the preference as racial. Among the numerous hypotheses advanced by that side of the debate is whether Congress could pass legislation prioritizing Native Americans for COVID-19 vaccines. Or whether lawmakers could make similar decisions for different races.

“You would agree, I believe, but tell me if you disagree, that Congress couldn’t give a preference for white families for white children, for Black families for Black children,” Associate Justice Brett Kavanaugh asked the Department of the Interior’s attorney. “And why is this different?”

Edwin Kneedler, the attorney, responded that the difference was due to Native Americans having a different political relationship with the United States government.

The high court’s three liberal justices and Associate Justice Neil Gorsuch, who has frequently disagreed with his conservative colleagues on tribal issues, both expressed support for the law. This support was based, in part, on Congress’ broad authority to govern the federal government’s relationship with tribes without interference from individual states. They claimed that the law was enacted in part to ensure the long-term viability of the nation’s tribes.

Associate Justice Elena Kagan stated, “The first thing you need for self-government is a functioning polity.” “And Congress expressly states in this statute that it believes this statute is critical to the tribe’s continued existence as a political entity.”

The lawyer representing non-Native families, Matthew McGill, countered that a child’s tribal membership is unaffected by placement. In other words, placing a Native child with a white family would not reduce the size of a tribe, he claimed.

At times, it appeared that some of the justices were looking for a specific outcome, focusing on specific provisions or debating whether the proper parties were involved in the case.

Before Congress passed the Indian Child Welfare Act in 1978, adoption agencies took hundreds of thousands of Native American children from their homes, sometimes forcibly, and placed them with non-Native families or in boarding schools.

Alarmed by the practice, Congress required people seeking to terminate parental rights in cases involving a Native American child to notify the biological parents and the tribe. When a Native American child is placed for adoption, the law also requires that preference be given to Native American families.

The appeal follows a deeply divided opinion from the United States Court of Appeals for the Fifth Circuit, which split evenly on several provisions of the law. The outcome upheld a federal district court’s ruling that certain provisions of the law are unconstitutional.

In the past, the law has divided the Supreme Court in unpredictable ways. A 5-4 majority sided with a 3-year-old girl’s non-Native adoptive parents in 2013 over a claim made by her biological father, a Cherokee Nation member who objected to the adoption after the fact. In an opinion written by Associate Justice Samuel Alito, a conservative, the court ruled that a noncustodial parent could not invoke the law.