Keyes v. The United States was a Supreme Court case that addressed the issue of whether the federal government had the power to enforce the Fourteenth Amendment's Equal Protection Clause in public schools. The case was brought by a group of African-American parents in Denver, Colorado, who alleged that the Denver public school system was segregated and that the federal government had failed to take action to desegregate the schools. The Supreme Court held that the federal government did have the power to enforce the Equal Protection Clause in public schools, and that the Denver school system was in violation of the Fourteenth Amendment. The Court also held that the federal government had the power to order the desegregation of the Denver public school system. The decision in Keyes v. The United States was a landmark ruling that established the federal government's power to enforce the Equal Protection Clause in public schools.

Justice Field delivered the dissenting opinion in Keyes v. The United States, arguing that Congress did not have the power to pass a law prohibiting racial discrimination in real estate transactions. He argued that this was an issue of local concern and should be left up to state legislatures or municipal governments. Furthermore, he believed that if Congress had such authority it would lead to further federal encroachment on states' rights and could potentially violate the Tenth Amendment's guarantee of reserved powers for states. He also noted that there were already laws against fraud which provided sufficient protection from any potential abuses by private parties involved in real estate transactions without needing additional legislation from Congress. In conclusion, Justice Field asserted his belief that allowing Congress to regulate matters traditionally within state control would undermine both constitutional principles as well as long-standing legal precedent concerning federalism and separation of powers between different levels of government