The aim of this paper is to analyse the issue of regulations against speculation and usury in the first years of the Second Polish Republic (1918-1920). The long period of World War I resulted in a major economic shock and long-lasting condition of shortages of commodities, including the necessities of life. This situation had a terrific impact on politics and forced the Polish legislator to react. As soon as 5 December 1918 a Decree on war usury was issued. The regulation in the field of war usury identified several types of illicit acts and contained basic rules of a particular procedure which was supplementary to the common penal procedures. Due to a low level of legislation, the regulation was defective and incoherent with the system of the law. Since the previous regulation was still in force, a dissonance between law on the books and law in action occurred. Furthermore, due to provisions contained in the Decree it was not possible to eliminate the discrepancy thanks to common rules of interpretation of legal texts such as lex posterior derogat legi priori.