Issues of conflict of laws in labour matters arise where the relations between an employer and a worker are liable to be affected by the legislation of two or more countries, whether this is the result of the employer and the worker having different nationalities or domiciles, of the worker being sent abroad by the employer for a more or less prolonged period, of the work being carried out in several countries (such as in international transport), of the employer having branches in several countries, or of a host of other eventualities. The variety of such situations and the number of legislations which may be involved have increased substantially in recent years. The question of conflicting labour laws is of particular interest to migrant workers and of daily relevance to undertakings that send workers abroad, have foreign subsidiaries or engage foreign labour; to workers' representatives in such undertakings and to unions bargaining with their management; to labour inspection services and other bodies concerned with the enforcement of labour law; and, of course, to the workers concerned.
Many of the conflicts and uncertainties inherent in the subject would seem to be due to the difficulty of establishing a clear dividing line between the legitimate scope of the law of the place of work and that of the home base (a difficulty compounded by such problems as that of identifying the true employer). The controversial issue of the choice of law by the parties may well be largely a reaction to that difficulty. Since there are already conflicts and uncertainty where these two basic systems confront each other, it is not surprising that the problems should be multiplied in cases in which a larger number of legal systems are involved, usually because there is no clear home base.
Under the rules of private international law there are two legal systems which have an important role to play in the labour field. One is that of the place of work: it is widely applied to the typical individual employment relation; its applicability is reinforced by the fact that much of it is mandatory and it is prime importance in collective relations. The second of these legal systems is that of a home base, often (though not necessarily) of both employer and employee: that system is applied not only to travelling personnel such as transport works and to certain categories of mobile managerial staff, but also to a considerable number of workers sent abroad for specific projects or assignments; certain connecting factors used to determine the law applicable to the typical employment relation (such as the common nationality or domicile of the parties, the place of business of the employer and even the place of conclusion of the contract) may lead to the adoption of that system; within its limits, it can apply to collective as well as individual labour relations.
Approaches differ from country to country, and reflect different types of foreign connections in labour matters. In many countries private international law is undergoing a wider process of evolution and reconsideration. There are two main reasons for this. On the one hand, on the national plane the law has to take account of growing state intervention in economic and social affairs; labour relations are one of the fields in which this factor is of considerable relevance. On the other hand, internationally there has been a development of practices and institutions, including the growth of multinational groups of companies, which did not fit in with traditional concepts. As a reflection of these developments, though not as a necessary result, the question is now also being asked in some countries, whether private international law, which had traditionally been seen as providing a neutral method of choosing the system of law to govern a particular relation (a method treating all systems of law as equivalent), should not be so applied as to further social concepts, in particular, by taking account in each case of the results of a choice of law.