International divorce is becoming more and more common. In any relationship breakdown there are often foreign connections such as nationality, residence, domicile and so on.
Between European Union countries (except Denmark) two or more countries may have jurisdiction under the Brussels IIa Regulation (part of the international procedural rules for matrimonial matters) to entertain a divorce.
Even if no country has jurisdiction it is possible to fall back on national law.
For example, let’s take an English husband and a German wife living in Hong Kong. The husband can divorce in England, potentially on the basis of domicile, and the wife in Germany on the basis of nationality. Hong Kong may also be a relevant jurisdiction.
However, if the husband and wife returned to England and Germany respectively and are habitually resident there, both could choose the jurisdiction within which they wish to divorce, i.e Germany or England.
The position is similar but different when outside Europe. An English husband living with a US wife (who is also Italian) in California could still divorce in England potentially on the basis of his domicile.
If, however, both parties have Italian nationality as well then Italy would have jurisdiction on dual nationality. If the husband relinquished Italian nationality then both England and Italy would have jurisdiction, not to mention the USA!
This is a complicated area of law but it is vitally important that in any international divorce case legal advice is taken, and in all the relevant jurisdictions so that potential outcomes for financial settlement (the rules about children are different) can be checked so a party can see what jurisdiction best suits his or her case.