Objectives:
The subject of this study is to interpret the provision of Ulpian from the 11th book of the commentary to the praetor’s edictie. Non capitur, qui ius publicum sequitur (D. 50,17,116,1). In Romanist literature, this provision is basically treated quite marginally. References to this provision are usually found in the footnotes, in order to exemplify some thought, but without an in-depth analysis.

Material and methods:
The explanation of the meaning of ius publicum used in the text will be crucial for the process of interpretation of this provision. One can initially assume that Ulpian using the phrase ius publicum did not mean public law from the systemic point of view, but the well-established and universally applied provisions of private law, regardless of their origin (jurisprudence, the praetor’s edict or the emperors’ constitutions).

Results:
Thus, the research hypothesis may be the statement that the application of the legal provisions of private law can not be the basis for the submission of an insidious or unfair act in a particular case. This is how the ambiguous verb capitur (from capio, cepi, ceptum) should be translated.

Conclusions:
Consequently, whoever exercises the law can not be impute bad faith. This principle has a great importance when determining the responsibility of persons performing public tasks in accordance with the law and the procedures envisaged.