Two years ago, I flagged up the issues of the effects of marriage on property rights, private international law and the proposed EU Regulation Rome IV.

In South Britain only, there is now the Marriage (Same Sex Couples) Bill (HC Bill 126). There has been much discussion as to the effects on religious organisations, but nothing on the difficult private international law (PIL) issues involved. The Bill proposes that in England and Wales, marriage of a same-sex couple shall be lawful.

While, personally, I support all measures of equality, I am concerned that the cross-border and EU issues arising from the current drafting have not been addressed.

Some EU states, such as Spain and Portugal, have not introduced registered partnerships at all. They permit marriage by both same- and mixed-sex couples and usually recognise a same-sex registered partnership as a marriage. Sweden and Norway have followed the Dutch example. Denmark (but not Greenland or the Faroes) also did so from 15 June 2012. The Republic of Ireland followed the UK and introduced civil partnerships on 1 January 2011, with a three-month registration period. The German and Dutch registered partnerships have exactly the same matrimonial property regimes as marriage. France is also debating same-sex marriage.

There are no current EU Regulations dealing with the recognition of marriage or registered partnerships. The 1978 Hague Convention XXVI has been ratified only by Australia, Luxembourg and the Netherlands.

The rest of us, therefore, have our own conflicting PIL rules. For most EU states, capacity to marry is governed by a citizen’s personal law. In the UK and the Republic of Ireland, that is the law of the domicile at the time of marriage. For most others, it will be the law of citizenship.

In France, while it is not possible to register a same-sex marriage, a foreign same-sex marriage is valid if valid in accordance with the law of the nationality of each party. A Dutch same-sex marriage is therefore valid in France if between two Dutch nationals, but not if between a Dutch national and a French national.

In states that have introduced same-sex marriage, it is usually recognised as valid if one party is a national or if both are habitually resident in the state that permits same-sex marriage.

It is Rome IV that has shown the main differences between registered partnerships and marriage.

Since only some states have registered partnerships, the only law that can govern the partnership is that of the place of registration. The law governing the property effects of marriage, on the other hand, is usually independent of the place of marriage and can be that of the common domicile, of nationality or of a common residence.

Section 38 of the Family Law (Scotland) Act makes it clear that the dual-domicile theory is in force in Scotland. The Marriage (Same Sex Couples) Bill does not currently appear to deal with any of these issues. If passed in its current form, the effects would seem to be:

• Same-sex marriage celebrated anywhere in the world will be recognised in South Britain as a valid marriage if each party is domiciled at the time of the marriage in a state that also recognises same-sex marriage, but not otherwise. Will this apply to marriages celebrated before the Bill is enacted? What will be the effect of a change of domicile in the interim? Such marriages will still be recognised as civil partnerships in Scotland and in Northern Ireland.
• Existing civil partnerships registered in South Britain could be converted to marriages, but only if each party is domiciled in a state that recognises same-sex marriage. Civil partnerships registered outside South Britain (including overseas relationships, but not foreign same-sex marriages) cannot be converted to marriage, even if celebrated between two people domiciled in South Britain.

Most of my clients haven’t got a clue what domicile means. If the registrar asks where a bride or groom is domiciled, and the answer is Scotland or Poland, what is the registrar to do? Proceed with a marriage that may not be valid or tell them to come back later?

Now that almost 40 per cent of people in London were born outside the UK, isn’t it time for the UK to ditch domicile and use habitual residence as the personal connecting factor?

There is no sign that these issues are going to be resolved any time soon. PIL is ignored at one’s peril.