The principle of party autonomy, known not only in the common law legal system but also in the civil law system, provides parties contracting in civil and commercial matters with the right to establish their own rules, as long as these rules do not contradict mandatory law. This right is presumed to be protected by the force of law. It follows, that when a choice of court clause is included in the contract, disputes are supposed to be solved by the court chosen by the parties.
This principle is not compromised by the Brussels I Regulation (or previously, the Brussels Convention). Moreover, it is repeated in its Articles 1 and 23. At the same time, the rule of lis pendens, provided for by its Article 27, aims to preclude subsequent actions in other Member States if a court is already seized and allows the appearance 'on the legal scene' of a court other than the court chosen by the parties. And the lis pendens rule prescribes the latter to stay proceedings until the court not chosen, but first seized, examines and declines its jurisdiction.