The evidence seems to support the theory that these rules were not uniformly enforced. But they were invoked against "troublesome" black residents, or they could be used against whole communities, as in Cincinnati, when white citizens found the increase in black population had reached an unacceptable level. They served blacks as grinding reminders of apartheid intentions and legal subjugation, and they offered white authorities and Northern mobs a cloak for harassment and violence.
Henry W. Farnam, “Chapters in the History of Social Legislation in the United States to 1860,” Washington: Carnegie Institution, 1938, pp.219-20.