1.The Government of the Federal Republic of Germany states, inter alia, the following:A — The principal purpose of Articles 31 et seq. of the Convention is to ensure that the decisions of the courts of other Contracting States may be declared enfordeable by means of a simpole and effective procedure and in the manner most favourable to the person seeking enforcement.It follows from the first paragraph of Article 33 of the Convention which provides that ‘the procedure for making the application’, that is to say the application for the issue of an order for enforcement (Article 31), ‘shall be governed by the law of the State in which enforcement is sought’, that the Convention has left it to national law to settle the questions which it has not dealt with itself. This explains why the procedure for enforcement of a foreign judgment has not been rendered equally simple by all the Contracting States, particularly as regards the costs. Thus, for example the German law in implementation of the Convention enables the applicant to bring proceedings without the assistance of an advocate, whereas that requirement is imposed under the laws of at least most of the other Contracting States. It may be asked whether the maintenance of such burdensome provisions is entirely compatible with Article 220 of the Treaty and with the spirit of the Convention particularly where, as in the present case, the result is that the simplified procedure for which the Convention makes provision is more expensive than a normal procedure by way of a main action.B — Apart from these considerations, the arguments for and against an affirmative answer to the question of the Hoge Raad are, it is argued, as follows:(a) The proposition that the procedure for which Article 31 of the Convention makes provision is exclusive can be based on the following considerations in particular:1. If this proposition were accepted, foreign orders for enforcement would be uniformly enforced throughout the field of application of the Convention. Thus the latter would be applicable to all aspects of proceedings to enforce a foreign judgment, for example it would be applicable as regards the protection that the Convention gives to a debtor against a definitive enforcement of a foreign judgment before the latter has itself become res judicata. The Convention would also apply as regards the limits that it sets on the enforcement of foreign judgments imposing fines, and would apply in so far as it enables foreign orders for enforcement to be partially enforced, lays down a common set of reasons for which recognition of a foreign judgment may be refused and, finally, enables the debtor to appeal against the decision to issue the order for the enforcement of the foreign judgment.2. The procedure for enforcement is simplified and accelerated, for creditors do not have to enquire whether any legal remedy exists other than the procedure laid down by the Convention.3. Contrary to other comparable international instruments, the Convention does not contain any provisions expressly enabling the creditor to sue any such other legal remedy.4. In any case it is the duty of each Contracting State to ensure that the procedure under Article 31 is always the most simple, the least burdensome and the most effective.(b) In support of the proposition that the Convention does not prevent the creditor from bringing a new action under national law, as has happened in this case, the following arguments, amongst others, may be advanced:1. The application of national law is only prohibited in so far as that prohibition results from the text of the Convention. Yet the Convention only requires the Contracting States to make the procedure for the enforcement of foreign judgments laid down by Article 31 et seq. available to the parties; it does not require that they must exclude other possibilities of obtaining the enforcement of debts for which there exists a foreign order for enforcement.This interpretation is indirectly confirmed by the first sentence of the second paragraph of Article 26 of the Convention which provides that any interested party ‘may’ use the procedure laid down by the Convention in order to obtain recognition of the foreign judgment. Therefore it is permissible for the national legislature to offer the said party other legal remedies leading to the same result.2. In general, an international convention should not necessarily be interpreted as meaning that the interested parties are bound to base their claims on that convention alone and not on any other legal basis, even a more favourable one. To hold otherwise would only be acceptable if the harmonization intended by the authors of the convention had absolute priority. Such is not the case here, for the principal objective of the convention is ‘the simplification of formalities governing the reciprocal recognition and enforcement of judgments of courts or tribunals’ (Article 220 of the EEC Treaty). Therefore, where there exists a national procedure which costs less than the procedure under Article 31, the Contracting States have no interest in imposing the latter on the interested parties. To leave national law free to complete the rules of the Convention in accordance with the spirit of the latter in certain circumstances not envisaged by its authors makes it possible to achieve flexibility of application which, in the interests of the interested parties, ought not to be excluded a priori.3. It is no objection to the argument put forward here that it is in any event only possible to bring a second main action in so far as the Convention accepts, as a general rule, the jurisdiction of the court before which the action is brought, that the proposition leads to ‘fortuitous’ results. For enforcement normally takes place at the place where the unsuccessful party is to be found and therefore Article 2 of the Convention applies to most cases. That article provides that in principle ‘persons domiciled in a Contracting State shall … be sued in the courts of that State’.Moreover, in any event, Article 21 of the Convention prevents a new main action from being brought before the procedure commenced in the first State has closed with a judgment which has the force of res judicata. The debtor is thus sufficiently protected.Finally, even within the context of a second main action, there is nothing to prevent the general rules of the Convention and the provisions thereof relating to the recognition of foreign decisions from being applied.C — In reality, the answer to be given to the Hoge Raad depends on whether Article 220 of the Treaty and the Convention looked at as a whole require the Member States to organize the procedure under Article 31 of the Convention so that it is the simplest, the most effective and the least burdensome. If there is no such obligation, then the conflict between the arguments respectively put forward in favour of the proposition that the said procedure is of an exclusive nature and in favour of the pluralist proposition results in a decision in favour of the latter. That proposition does not seriously jeopardize the uniformity of the procedure for enforcement of foreign judgments within the Community for it is only in rare cases that it is possible to bring a new main action. Moreover the proposition is in accordance with the fundamental objectives of the Convention. In particular, allowing the procedure laid down by Netherlands law and chosen by De Wolf has advantages for interested parties in other Contracting States in disputes involving very small sums.Therefore the answer to the question of the Hoge Raad should be as follows:The fact that under Article 31 of the [Convention] an order for the enforcement of a decision emanating from one Contracting State may be requested in another Contracting State does not prevent a new action concerning the same subject-matter as the action brought in the first Contracting State from being brought between the same parties in the other State, if the new action, based on the judgment emanating from the first State, which must be recognized (Article 26), tends to give effect to the individual right claimed more simply or more easily. Moreover in so far as the new action is admissible under Article 2 et seq. and Article 21 of the Convention, the national law of the other Contracting State determines the legal criteria according to which that new action may be brought in that State on the basis of the judgment of the foreign court, as an exception and despite the existence of that judgment.