In the case of Williams, Treasurer of Oklahoma, et al. v. Moss et al., 1963, the U.S Supreme Court ruled in favor of Moss and other African American parents who had filed a lawsuit against Oklahoma's school voucher program on behalf of their children. The plaintiffs argued that the state's voucher system was discriminatory as it allowed white students to use vouchers at private schools while denying this opportunity to black students due to segregation policies prevalent in many private institutions at that time. The court held that such an arrangement violated equal protection clause under Fourteenth Amendment since it facilitated racial discrimination by indirectly funding segregated schools through public money allocated for education purposes. Therefore, any state action leading to or supporting racial segregation was deemed unconstitutional even if it involved indirect means like educational vouchers.

In the dissenting opinion for Williams, Treasurer of Oklahoma, et al. v. Moss et al., Justice Harlan argued that the majority's decision to strike down an Oklahoma law requiring loyalty oaths from state employees was incorrect. He contended that such a requirement did not violate First Amendment rights as it merely sought assurance of allegiance to the United States and its Constitution - something inherently expected from public servants anyway. Furthermore, he believed that this oath could serve as a deterrent against potential subversive activities within government ranks and thus contribute towards national security interests. The justice also expressed concern over what he perceived as judicial overreach by his colleagues in invalidating state laws without sufficient constitutional grounds or compelling reasons.