Read the following excerpt taken from the US Supreme Court case Plessy v. Ferguson (1896).

The case coming on for a hearing before the Supreme Court, that court was of opinion that the law under which the prosecution had was constitutional, and denied the relief prayed for by the petitioner. Ex parte Plessy, 45 La.Ann. 80. Whereupon petitioner prayed for a writ of error from this court, which was allowed by the Chief Justice of the Supreme Court of Louisiana.
MR. JUSTICE BROWN, after stating the case, delivered the opinion of the court.
This case turns upon the constitutionality of an act of the General Assembly of the State of Louisiana, passed in 1890, providing for separate railway carriages for the white and colored races. Acts 1890, No. 111, p. 152.
The first section of the statute enacts
"that all railway companies carrying passengers in their coaches in this State shall provide equal but separate accommodations for the white and colored races by providing two or more passenger coaches for each passenger train, or by dividing the passenger coaches by a partition so as to secure separate accommodations: Provided, That this section shall not be construed to apply to street railroads. No person or persons, shall be admitted to occupy seats in coaches other than the ones assigned to them on account of the race they belong to."
The Supreme Court’s ruling in Plessy v. Ferguson was problematic because
the court was not able to overturn the Louisiana state law that required passengers be separated by race.
the court did not have any Black justices among its members.
it was unclear if Plessy (who was of mixed race) broke the law by sitting in the whites-only coach.
it was based on the belief that segregation was permissible as long as the facilities were equal.