The subject of this paper is legislation against war usury in the early interwar period. There is no wide analysis of this topic in existing legal literature. This article is multifaceted – it is based on administrative regulations as well as on penal rules. Regulation in the field of war usury consisted of several types of illegal acts and basic rules of a particular procedure which was supplementary to common penal procedures. For a more complete overview of the main problem the author presents sentences handed down in court decisions and opinions of legal scholars. During the rebirth of the Republic of Poland matters of speculation, defined as “war usury,” were one of the most controversial legal problems. Shortages of scarce goods were causing anxiety in Polish society. At the time uncontrolled trade in scarce goods could result in economic turmoil and serious social unrest. Regulations in both the decree of December 5, 1918 and in the Act of July 2, 1920 were clearly edited and thus caused few difficulties in interpretation. However, since there were three different criminal procedure systems in force in Poland at the beginning of the twenties, application of procedural regulations was frequently problematic. The most difficult problem of interpretation was directly connected to imprecision of legal terms, including the term “war usury.” Scientific analysis of the problem should lead to more accurate knowledge of the interwar Polish legal system and will be a contribution to comparative study in contemporary Polish regulations.