AN ‘INTELLIGIBLE FIELD OF STUDY’

Constitutional law may be considered the most important part of public law, beside criminal, fiscal and administrative law, and the law of nations, and it seems advisable at the outset carefully to define our field of study.

Definition of the subject

The concept of public law is itself somewhat problematic. It is true that Roman law expressly distinguished ius privatum and ius publicum, but the latter appears, on closer examination, not quite to cover the same ground as present-day notions of public law. Indeed, we read in Justinian's Institutes that ‘publicum ius est, quod ad statum rei Romanae spectat, privatum quod ad singulorum utilitatem pertinet’ (1, 1, 4) (‘public law is concerned with the Roman state, private law belongs to the utility of individuals’), and the Digest, the most important part of Justinian's Corpus Iuris Civilis, goes on to explain that ‘publicum ius in sacris, in sacerdotibus, in magistratibus consistit’ (1, 1, 1, 2) (‘public law concerns sacred things, priests and magistrates’). This definition is, to modern lawyers, incomplete as it omits, inter alia, criminal law. Elsewhere the Corpus Iuris mentions ius publicum in a sense that reminds us of the modern notion of public order: for example where the Digest (28, 1, 3) explains that the form of a testament is a matter ‘non privati, sed publici iuris’

The rise of the patrimonial concept of the state in the Middle Ages meant that this fundamental dichotomy was lost.