The NAACP had been building its legal strategy for decades. The 1931 Margold Report, commissioned by the organization and written by Nathan Margold, had outlined a legal theory for challenging school segregation: rather than accepting the separate but equal framework and arguing that separate Black schools were inadequately funded (the gradualist approach), the organization should challenge the constitutionality of segregation per se — the proposition that separate facilities violated equal protection regardless of their relative quality. This was the more ambitious and more legally challenging argument, but it was the argument that could actually end segregation rather than just require better funding for segregated schools.
Thurgood Marshall and Robert L. Carter filed an amicus brief in Mendez on behalf of the NAACP. The brief advanced the segregation per se argument: that segregation itself, independent of physical conditions, violated the Fourteenth Amendment’s equal protection clause. The Mendez case offered an opportunity to make this argument in a federal court with a plaintiff class of children from a different racial background than the NAACP’s primary constituency.
The JACL’s amicus brief connected the case to the Japanese American experience of wartime incarceration and to the organization’s broader civil rights commitments. The American Jewish Congress and the ACLU also filed amici, reflecting the emerging coalition of organizations that saw school segregation as a constitutional problem requiring a concerted legal response.
LULAC, the League of United Latin American Citizens, had been working on civil rights issues affecting Mexican Americans for decades and helped with organizing and support around the case. The organization’s presence reflected the community infrastructure that existed before and around the litigation.