Adoption law, like most areas of family law, is primarily governed by the states. However, federal regulations can oftentimes be intertwined with state law. The Indian Child Welfare Act is a good example of federal family law that will govern state laws.
ICWA is a federal law passed in 1978 that seeks to keep Indian children with Indian families. The law creates federal requirements that apply to state child custody proceedings. These federal requirements occur when the proceeding involves an Indian child who is a member (or eligible member) in a federally recognized Indian tribe.
Source: Adoptivefamilies.com