Legal effect of the principles of UNIDROIT international commercial contracts

The article considers particular ways in which the UNIDROIT Principles come into legal effect. Parties’ selection of the Principles as rules of law governing the contract can be considered as incorporation of the rules into the contract or as a selection of law with the exclusion of any national law. The author supports the first approach. In international commercial arbitration the Principles can be applied without any references in the contract; however, in this case their legal effect is based on the implied will of the parties which is determined by the circumstances of the case.