In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.
Q: Plessy argued that the state law which required East Louisiana Railroad to segregate trains had denied him his rights under the Thirteenth and Fourteenth Amendments to the United States Constitution .
A: 
The State of Louisiana " , Plessy 's lawyers argued that the state law which required East Louisiana Railroad to segregate trains had denied him his rights under the Thirteenth and Fourteenth amendments of the United States Constitution , which provided for equal treatment under the law .