Furthermore they used the 14th and 15th constitutional amendments in an attempt to protect the rights of individuals in their favour; the amendments stated that citizenship rights and voting rights were to be guaranteed to all who were born in the USA, regardless of their race. Moreover American citizens could take the government to court in cases where it appeared they had acted in a way to challenge any constitutional right. Experienced lawyers, such as Thurgood Marshall, were used by the NAACP to support the cases where citizens took the authorities to court, two such successful cases were Morgan v.s Virginia (1946) and Smith v.s Allwright (1944). Morgan v.s Virginia (1946) challenged segregation on interstate on bus services, in 1944 Irene Morgan was fined $100 for refusing to give up her seat on an interstate bus. They argued that since an 1877 supreme court decision ruled that it was illegal for a state to forbid segregation, then it was likewise illegal for a state to require it, and in result the Supreme Court agreed. This can be clearly linked to Rosa Parks as the story is matched, but this is important as shows how much more attention the NAACP had collected in later years when the same incident happened to Rosa Parks who was made famous from the event. This is significant to the extent of achievement of the NAACP as it shows how they progressed in making it a known campaign over 11 years. Similarly fought for by Marshall in the Supreme Court, the Smith v. Allwright case outlawed all-white democratic primary elections throughout America. Cases such as these were significant because they demonstrated that organisations such as the NAACP were able to achieve successful steps to ending segregation through non-violent action.
Additionally the NAACP used non-violent direct action as a successful means of tackling segregation. An example of this is the Montgomery Bus Boycott (1955 - 56) in which the blacks of Montgomery boycotted the local buses. This was following Rosa Parks’ arrest, to show the importance of black customers by financially damaging the bus companies. Moreover, the NAACP targeted education because it was easy to show that while children were being separately, they were not being educated equally. This gives a clear indication towards the Jim Crow laws which stated “separate but equal” belief, this is significant to the NAACP as it shows them legally challenging them against education board. In 1954, the Supreme Court decided the landmark case of Brown v. Board of Education of Topeka. The segregate schools were concluded that they are "inherently unequal” by the Supreme Court. The Court found support for its decision in studies that indicated that minority students learn better in racially mixed classrooms. The next year, in Brown II, the Court announced a decision outlining its plan for implementing racial desegregation in the schools. The Court took a cautious approach, remanding the cases to district courts with orders to integrate the schools "with all deliberate speed”. In extent the NAACP achieved its aim to challenge the education board but also did not actually achieve any movement towards de-segregated schools until Little Rock High School. Once again this is significant as it shows how after time the NAACP actions become effective and gives the NAACP a sense of achievement but only in later years of legal battles between the Supreme Court.
In conclusion the extent of achievement by the NAACP only began to have a successful bus boycott to end segregation in 1955. Up till then, the NAACP wasn't very successful in enfranchising blacks, or ending segregation. In many ways the NAACP use effective a strong legal case to fight on behalf of African Americas.