Due to the decline in marriage rates, the institution of the De Facto Couple has become an important issue in recent years. In fact, the De Facto Couple can be defined as the union between two people who want to live stably in a relationship similar to the conjugal union.

Despite their increasing frequency and acceptance by society, their international regulation still gives rise to considerable doubts. What happens if one of the parties is foreign? What legal system applies to them and before what court can claims be made?

In the absence of international regulation of this subject, our courts have been applying different solutions according to the situation:

1º.- In the case of “registered non-marital couples” (also called “formal” De Facto Couples), the law of the country in which the couple has enrolled for the first time shall be applied. The existence of the union, the relationship between the parties and the dissolution of the union shall all be regulated by this law.

2º- In the case of so called “informal couples” (not registered), the common national law of the parties should be applied (ex art. 9.1 of the Spanish Civil Code).” In the absence of a common law, the most convenient solution is to apply the law of the country with which the parties have the closest link, usually applying the law of habitual residence (in our case Spain).

3.-F or all those external effects arising from the existence of the De Facto Couple (hereditary effects, maintenance, etc.), the corresponding rules for International Private Law shall be applied, and the national law to be used shall be determined in this fashion.

It is important to note at this time that, due to the recent nature of the subject, the Spanish courts frequently choose to apply the Lex Fori (Spanish law), as has been the case in the judgment of the Provincial Court of Barcelona of November the 3^rd 2004, turning a blind eye, therefore, to the international dimension of the subject.

Faced with this phenomenon, the CIEC has developed an International Convention on the recognition of registered De Facto Couples, signed in Madrid on September the 5^th 2007, whose ratification by Spain will mean major changes in the international regulation of De Facto Couples.