In the context of a financial market, investors are the principals who, through their intermediaries, preside over market operations. Their relationship with the financial markets is the chosen domain of the lex mercatus. The law of the financial market has a strong application here, based on the objective it pursues: the proper functioning of the trading platform. This function of the law of the financial market makes it possible to group the rules that pursue it into a single category, the lex mercatus. The application of these rules is triggered by the use of the trading platform; their connecting criterion is that of the platform itself,which we have endeavoured to define.Such a category is likely to be included in a bilateral conflict-of-laws rule according to which:

‘The rules relating to the operation of the financial market shall be subject to the law of the trading venue.’

Firstly, it is possible to include the rules relating to the obligations of market members towards the financial market. These rules no longer make it necessary to subject the contract concluded with their clients to the law of the market, but they continue to ensure their protection through the rules of conduct that are imposed on members (Chapter 1). The application of the lex mercatus is most evident in the regulation of market transactions. Although the concept of market operation has replaced that of stock exchange operation, it nevertheless continues to designate the mechanism that ‘consists in the production and execution of the order on the market’.