As a rule-making entity, the Union is oft en confronted with the rival claims of regulation of the Member States, which want to keep control of the matter at issue and invoke their sovereignty. Is the regulation of cross-border situations relating to third States and the determination of the external scope of EU measures a matter for EU law or for the national law of the Member States? Here again there surfaces the triangular nature of private law in the Union. In every legal relation governed by private law, three actors are present: the private parties, the European Union and the involved Member States; and in each case it is the private parties –who are the key actors in private relations –that must take into account the regulatory claims of the latter two figures.

Where the Union itself determines the scope of territorial application of EU private law, the respective scope rule takes precedence over national conflict rules. On the other hand, the absence of an EU rule on the external reach of a provision of EU private law may have several meanings. It may constitute a lacuna which the Court of Justice feels bound to fill. It may also leave the determination of the external reach to the Member State(s) involved. It may finally signal a lack of interest on the part of the Union in the enforcement of a given item of legislation in cases connected with third States. Chapter XXXV will further elaborate on the unilateral scope rules adopted by the Union and will provide evidence of the EU’sdetermination to secure a wide scope of application for its law.

Attempts at an expansive unilateral enforcement of law invariably collide with corresponding unilateral attempts of foreign States and entities. The resulting collision may be positive , i.e. an overlap of the regulations associated with a special case; it may also be negative in the sense that none of the regulations involved applies to the case. Such collisions give rise to eff orts of synchronisation through international treaties.