having extensive experience in civil rights legislation, he worked for the national association for the advancement of colored people (naacp) during the 1940s and 1950s to advance their goal of overturning the 1896 supreme court decision plessy v. ferguson, which had legalized segregation of public facilities by race under the doctrine of "separate but equal". he helped to prepare legal arguments and advised the naacp teams that were drawing up briefs, testing presentations, and holding moot court exercises. this work eventually culminated in the 1954 supreme court decision in "brown vs. board of education", which found that racially segregated schools were unconstitutional because they were "inherently unequal."