legal can of worms.
But David Cameron's new proposed same sex marriage law may change the nature of marriage beyond even his wildest imaginings.
Currently marriage and same sex civil partnerships are dealt with under two different types of legislation.
The formalities of marriage are predominantly governed by the Marriage Act 1949, the Marriage Act 1983 and the Marriage (Registrar General's Licence) Act 1970.
By contrast the Civil Partnership Act 2004 (CPA 2004) defines civil partnership as a formal legal relationship between two people of the same sex but gives same-sex couples virtually all of the rights and privileges of married couples.
The President of the Family Division has even described civil partnerships as conferring ‘the benefits of marriage in all but name’.
There are however some differences in English law, between a marriage and a civil partnership, but these differences focus not on the rights they confer, but on the genders of the partners, the procedure and place where the partnership is formed, and the roles of consummation and adultery in making and breaking the relationship.
These differences are there because they are different types of relationship. It is not ‘one size fits all’.
Currently same-sex couples cannot get married and opposite-sex couples cannot form civil partnerships.
One of the most intriguing mysteries about David Cameron’s plans to redefine marriage to include same sex couples was always therefore going to be how he would deal with ‘consummation’ and ‘adultery’.
At present a marriage can be declared void if it is not ‘consummated’. And if necessary, whether consummation has been achieved needs to be determined by medical examination. But how is a lesbian or gay marriage to be consummated? Interesting question!
In the same way adultery is grounds for divorce, but the legal definition of adultery is based on (how does one say this politely?) a certain kind of genital contact. So how exactly do lesbian or gay couples commit adultery? Or are the consummation and adultery definitions just to be dropped?
This is important because when a marriage breaks down, and the bickering over who has a right to what begins (in terms of possessions, money, children etc), then the outcome could depend, at least in part, on whether or not the marriage has been consummated and whether or not there has been adultery.
So how would Cameron deal with this problem?
Well now that the Marriage (Same Sex Couples) Bill has been published we finally know.
There will be no consummation or adultery for same sex couples.
The explanatory notes are more explicit than the Bill itself on this point with respect to consummation:
‘108. Paragraph 4 [of Part 3] amends section 12 of the Matrimonial Causes Act. The effect of this amendment is that non-consummation (either by reason of incapacity or wilful refusal) cannot be a ground on which a marriage is voidable for a same sex couple. The provisions for opposite sex couples remain unaltered.’
And adultery? Well it will simply not exist for same sex couples.
Under the Government's draft Bill only infidelity between a man and a woman constitutes adultery.
So while the law would give same-sex couples the right to marry, they would not be able to divorce their partner on the basis of adultery if their spouse went on to be unfaithful - unless they cheated with somebody of the opposite sex.
It also states that a straight person who discovered their husband or wife had a lover of the same-sex could not accuse their unfaithful partner of adultery in a divorce court.
So what does this mean?
First that this supposed equal marriage for same sex couples is not equal at all because in traditional marriage there is consummation and adultery and in same sex marriage there is not.
Second, this will mean that as soon as the ink is dry on the new law – assuming it passes – it will be ripe for attacks by people who might want, for whatever reason, to abolish consummation and adultery for traditional marriage as well on grounds of equality.
Imagine the following scenario. A man marries a wealthy heiress with no intention to consummate – she dies and the man claims his inheritance. The Estate argues that the heiress was in the process of getting an annulment for non-consummation. The man says he is being discriminated against because he is a heterosexual. If he was gay there is no requirement for consummation – what about his human rights?
According to the Daily Mail, lawyers and MPs have already argued that the distinction over adultery - which arose after Government legal experts failed to agree on what constitutes sex between same-sex couples - would cause confusion.
They warned it would create inequality between heterosexual and homosexual married couples who found themselves in the divorce courts, and said it would likely result in adultery being abolished altogether as a grounds for divorce.
Third, it means that same-sex marriages will, in effect, be legal open marriages. As long as both partners consent in a same sex marriage, each of them can have as many sexual partners as they choose, as long as they are all of the same sex, without actually ever committing adultery. This may actually suit some couples but it completely alters the meaning of marriage which is based on sexual faithfulness.
In fact since one is married without consummation, the situation might arise where a married member of a same sex couple could have sex with any number of people he is not married to (provided they are of the same sex) without ever committing adultery (because it doesn’t exist for same sex marriages) and without ever actually having sex with his or her married partner.
So for same sex couples, sex will be legally uncoupled from marriage altogether. And if there is a legal challenge on the basis of equality, the same thing may follow for traditional marriage.
I wonder if anyone has yet explained this to David Cameron?
I suspect he may be in for a few extra late night briefing before second reading on 5 February.