San Francisco had an ordinance that vested in the board of supervisors the discretion to grant or withhold their consent to the use of a wooden building as a laundry. Yick Wo (P) was imprisoned for violating that ordinance. P had been engaged in the laundry business on the same premises for 22 years, and fire wardens and health officers had inspected his facilities and found them to be proper. The city claimed that the ordinance that put P in jail was to protect the public against the dangers of fire. There was no such purpose on the face of the statute. P applied for a writ of habeas corpus. The board used the ordinance to deny all Chinese who applied for such a license but only denied one of 80 non-Chinese.