This was a ruling on the fourteenth amendment in relation to Chinese-Americans. The basics are San Francisco put in legislation to ban laundry facilities that were in wooden house. Currently 95% were in wooden houses and were overwhelmingly Chinese. When these people came to apply for permits, the Chinese were denied except for one of them, while 200 non-Chinese were approved. The law was overturned by the Supreme Court because of its overreach and clear abuse of authority, especially to exclude Chinese workers from this trade for no reason other than them being Chinese.
