A story from Canada is interesting and does demonstrate the dangers of reformers trying to achieve their ends though the Courts and Human Rights instruments rather than by democratic legislative change.
Back in 2003, in the case of Halpern et al. v. Canada brought by a number of same sex couples who had been refused the right to marry, the Ontario Superior Court ruled that the common law definition of Marriage violated the Canadian Charter of Rights and Fundamental Freedoms which is similar in terms to the European Convention on Human Rights. The Common Law definition of marriage was laid down by Lord Penzance in the case of Hyde v Hyde (1866) LR 1 P&D 130 (which involved the question of whether a Polygamous Mormon Marriage was recognised by the English Courts) as follows
"I conceive that marriage, as understood in Christendom, may for this purpose be defined as the voluntary union for life of one man and one woman, to the exclusion of all others"
Similar logic was used by the US Supreme Court in the case of Reynolds v. U.S., 98 U.S. 145 (1878) which also involved Mormon polygamy
Following the Halpern Case similar decisions were arrived at in other Canadian Provinces and this led to the Canadian Supreme Court decision in Reference re Same-Sex Marriage  3 S.C.R. 698, 2004 SCC 79 which agreed that the common law definition of marriage discriminated against same sex couples though the Court also held that Charter also protected Religious ministers from being forced to officiate at same sex marriages.
The decisions of the Canadian Courts were of course only focused on the question of same sex marriages but what the courts ignored was the fact that by destroying the Common Law definition of marriage they left the entire question of what marriage actually is completely up in the Air and that problem has now come home to roost.
In the Canadian case of Blackmore v. British Columbia (Attorney General), 2009 BCSC 1299 (CanLII) the question has been raised whether the Halpern etc decisions mean that Polygamy is now legal and the Criminal offence of Bigamy illegal
Winston Blackmore and James Oler are leaders of a polygamous Mormon splinter group in Bountiful, near Creston, British Columbia, and are accused of being married to more than one woman at a time. (The Mormon Church banned Polygamy in 1890 though some splinter groups have always continued the practice)
They were were charged with polygamy in January of this year after a two year investigation by the Royal Canadian Mounted Police. Blackmore was charged with marrying 20 women, though he claims to have had 26 wives and more than 108 children. Oler was charged with marrying two women.
Section 293 of the Canadian Criminal Code says that anyone entering into a conjugal relationship with more than one individual at the same time is in violation of the law.
On at least two previous occasions the RCMP had recommended that arrests be made, but the Crown denied the recommendation, saying that the ban on polygamy would likely be struck down on the basis of the Canadian re-definition of marriage to include homosexual couples, and the Charter's guarantee of religious freedom. After all once you have redefined "Marriage" away from being the union of one man and one woman where does redefiniton end, Polygamy, Polyandry, multi-person multi sex unions all potentially can lay claim to the title "marriage" and the end result will be the end of the idea of marriage itself as a legal concept because if any relationship can be classified as marriage, the eventually marriage itself ceases to have meaning.
In Britain of course we have not dropped the common law definition of marriage and Same Sex Civil Partnerships are legally distinct from marriage so of course what has happened in Canada could never happen in Britain. I wonder ??