 However, the manner of performance of the contractual obligations may differ according to the "lex loci solutionis".The proper law of the contract governs virtually all aspects of the contract, including its essential validity, nature, content, mode of performance and interpretation.By way of exception, however, the contractual capacity of the parties, together with the formalities of execution, are governed by the "lex loci contractus", unless the contract concerns immovable property, in which case the law of the country where the property is situated (the "lex situs" or "rei situae") applies.