What general principal was established with the Plessy v Ferguson Supreme Court decision

States cannot prevent African-Americans from voting
States could be punished with decreased congressional representation if they did not allow African-Americans to vote
States require separate facilities for African-Americans as long as the facilities were equal
States could not use taxes and literacy test to establish voting eligibility

The general principle established with the Plessy v Ferguson Supreme Court decision was that states could require separate facilities for African-Americans as long as the facilities were equal. This decision ultimately led to the "separate but equal" doctrine, which justified segregation and racial discrimination in public spaces.