A law prioritizing the placement of Native American foster children with their tribe has been challenged by a suit in Arizona.

As the Arizona Republic reports, Goldwater Institute has filed a class-action suit in Phoenix, AZ, calling aspects of the 37-year-old Indian Child Welfare Act unconstitutional. The suit alleges that the portions of the law relating to children living off-reservation prioritizes placing foster or adoptive children with their tribe over the child’s well-being.

Two families are featured in the case, both of whom attempted to adopt a Native American child only to have their efforts blocked by the law. The suit writes that, “alone among American children, their adoption and foster care placements are determined not in accord with their best interests but by their ethnicity.”

Arizona currently has 1,336 Native American children living in out of tribe placements. If successful, the suit could provide permanent housing for many of them.

The suit names the Federal Bureau of Indian Affairs, the U.S. Department of the Interior, and the Arizona Department of Child Safety as defendants. The Department of the Interior has indicated they will defend the law, as assistant secretary Kevin K. Washburn argued that it was still needed to prevent “unwarranted” removal of Indian children from their homes.

The Department of Child Safety stated that they would have no formal comment until the suit was resolved.