The paper presents a minimal extension of classical logic. The extension covers, mainly, (i) an introduction of legal regulations conceived as specific elements of provisions in legal rules; and (ii) an introduction of the application operation on legal regulations. Such an operation transforms a legal regulation into an empirical proposition describing some desired state of affairs. Moreover, it is assumed that legal arguments may contain two kinds of premises: a) legal regulations; and b) statements of empirical fact as a legal reality. A typical case of b) includes statements expressing the application or non-application of legal regulation in certain circumstances. Due to the distinctions introduced, the extended system of classical logic makes possible to analyse the logical structure of perfect norms as pentatomic. Although such a system is far remote from sophisticated systems of deontic logics, it is almost completely sufficient for lawyers’ practice.