The answer is the right to vote.
Jim Crow laws enforced racial segregation in public schools, but they did not outright deny African Americans the right to an education. Instead, they mandated separate schools for black and white students, which were often unequal in quality.
Jim Crow laws included measures such as literacy tests, poll taxes, and grandfather clauses that effectively disenfranchised African Americans, denying them the right to vote.
Jim Crow laws enforced segregation in public transportation, including trains, but they did not deny African Americans the right to travel. Instead, they required separate accommodations for black and white passengers.
While African Americans faced significant legal and social obstacles, they were not legally denied the right to challenge laws. However, the judicial system was often biased, making it difficult for them to succeed in such challenges.