...slavery nor involuntary servitude in the said territory, otherwise than in the punishment of crimes. . . Provided always, That any person escaping into the...lawfully claimed in any one of the original States, . . . may be lawfully reclaimed, and conveyed to the person claiming his or her service as aforesaid."...

...slave owners had the right to reclaim their fugitive slaves. Under this law, "any person escaping ... from whom labor or service is lawfully claimed in...claiming his or her labor or service as aforesaid." This provision of the ordinance wasn't exactly a new one but simply reflected Article IV, Section 2...

...nor involuntary servitude in the said territory, otherwise than in the punishment of crime, whereof the party shall have been duly convicted: Provided...any person escaping into the same, from whom labor may be lawfully elaimed in any one of the original States, such fugitive may be lawfully reelaimed...