Why was homer plessy arrested for why?

Homer Plessy was arrested for violating Louisiana's Separate Car Act of 1890, which mandated racial segregation on public transportation. As a mixed-race individual, Plessy deliberately sat in a "whites-only" railway car to challenge the constitutionality of the law. His arrest sparked the landmark Supreme Court case Plessy v. Ferguson, which ultimately upheld the principle of "separate but equal" and legalized racial segregation in the United States.