One of the purposes of the article is to provide an up-to-date account for the Romanmaxim jura novit curia (the court knows the law). Traditionally jura novit curia means thatthe court alone is responsible for determining which law applies to a particular case,and how without being limited to the legal arguments advanced by the parties. On thebasis of the systematic investigation of different elements of legal technology (legalfictions, principles, axioms or presumptions) the author formulates the conclusion thatjura novit curia can be attributed to the general legal presumption, which is related tothe characterization of law enforcement activities of state bodies. Moreover, taking intoaccount the interconnection of presumptions and principles of law, the author indicatethat there is a corresponding functional principle of legality to the presumption juranovit curia. In the second part of the article the author criticizes scientific assessment ofthe presumption of jura novit curia as confirmation of position on the exclusion of legalknowledge from the scope of special ones. It was argued in favor of legitimation of thelegal advices on interpretation and permissible application of law in order to increase thedegree of probability of the presumption of jura novit curia. Other substantial elementsof the presumption of jura novit curia, namely, an initiative and independent study of therules of law by the court without being limited to the legal arguments advanced by the parties do not conflict with the possibility of a court to get legal advices from specialistswho do not intervene the competence of the judge making the final decision. In the thirdpart of the article, the author finds the arguments for exclusion maxim jura novit curiaform foreign laws are not conclusive. It may be suggested that this assumption can leadto the negative consequences that can be expressed in the unreasonable restrictionof the application of foreign law. On the basis of the analysis it is possible to indicatethat jura aliena novit curia is the branch presumption of the international civil process,which correlates with the content of the principle of legality and the principle of theinternational civil process — the establishment of the content of foreign law ex officio.The author reasons that ignoring presumption of jura aliena novit curia obviously leadsto difficulties for the principle of applying foreign law ex officio, since it is impossible toapply foreign norms based on presumption jura non aliena novit curia. The presumptionof jura aliena novit curia should cover not only the content of foreign law, but also severalconditions for its application based on national law. The article challenged the theory thatthe requirement to apply foreign law in the same way as it is applied abroad is the fiction.The author justified that the notion of “foreign law” can be attributed to the fictions takinginto account that the court can apply only private foreign law and some foreign proceduralrules with considering national law restrictions.