The article provides an overview of the historiographical debates on the relevance of law and courts for colonial slavery in the early modern, presenting several possible master narratives. Departing from the question about the legal sources used by the jurists of the early modern era producing “slave law in action”, the article focuses on procedural law of the freedom trials, especially on the interim situation of the person whose status the trial was about. This aspect of the proceedings is fascinating, because here the tension between the two extreme positions of the parties (liberty vs. slavery/property) is discharged for the first time. A close look at the sources proves that the jurists sought to justify the possible solutions not only with the custom of the courts (stilus curiae), but that a variety of legal formants contributed to colonial slave law, notably the authority of the Roman model, which the article presents shortly in its development, and of certain medieval forms, like the summariissimum or the actio (or execeptio) spolii. Legal doctrine was frequently quoted. As a result, Brazilian colonial slavery did not occur in a legal vacuum, but proves to have been highly institutionalized, and many aspects of the civil law of slavery appear as a relatively conservative continuation of European practice, without visible innovations to the favor or the detriment of the unfree population.