Coalition for Marriage, the UK version of National Organization for Marriage, posted a video last week claiming that passage of the UK equal marriage bill will lead to the legalization of polygamous marriages in England and Wales.

On Feb. 5 the House of Commons overwhelmingly approved the equal marriage bill by a vote of 400 to 175.

The video, titled “Further Redefinitions“, is the third in CFM’s Marriage Minutes series.  CFM’s Marriage Minutes series appears to be a retread of NOM-Minnesota’s Marriage Minute series.

“Many people warn that once the ‘one man, one woman’ definition of marriage is removed, then society will be more ready to accept further redefinitions of marriage such as polygamy,” presenter Dr. Sharon James claims.  “If you move the definition of marriage away from the natural union of man and woman, there’s no logical reason to stop there. That’s what the evidence says.”

In truth, the evidence does not support this “slippery slope” assertion, a perennial favorite among opponents of civil marriage equality.

Not a single country that has legalized civil marriage for same-sex couples has gone on to legalize polygamous marriage.  Countries that have legalized civil marriage for same-sex couples are Argentina, Belgium, Canada, Denmark, Iceland, Netherlands, Norway, Portugal, South Africa, Spain and Sweden.

On the contrary, there is a great deal of overlap between countries that criminalize homosexuality or same-sex marriage and countries that have legalized polygamous marriage.

Source: Wikipedia

One equal marriage country, South Africa, does recognize polygamous marriages under customary law. However, this recognition is a result of the Recognition of Customary Marriages Act of 1998, a law passed eight years before same-sex couples could marry in South Africa.

In the CFM video, Dr. James neglects to mention that, for the purpose of calculating welfare benefits, the UK already recognizes polygamous marriages that were conducted legally in other countries.

As with South Africa, the United Kingdom recognized polygamous marriages before legalizing marriage for same-sex couples.

Ignoring these legal realities, the CFM video instead points to one isolated case each in the Netherlands and Brazil for “proof” that same-sex marriage leads to legalized polygamous marriage.

In the video, Dr. James tells us that in 2005, a man named Victor de Bruijn and two women signed a “three-way cohabitation contract” in the Netherlands.  This is true.  However, Dr. James fails to note that their living-together contract (“samenlevingscontract“) isn’t a legal marriage or even a registered partnership.  Only two unrelated adults not already in a marriage or registered partnership may marry in the Netherlands, according to the Dutch government’s website. While same-sex marriage has been legal for almost 12 years in the Netherlands, polygamous marriage remains illegal.

“Brazil having introduced same-sex marriage has now legalized a threesome union,” Dr. James goes on to say.  In August, 2012 a notary public granted a “uniao poliafetiva“, or “polyfidelitous union” to a man and two women.  There is disagreement among Brazilian legal scholars as to the legality of the uniao poliafetiva, according to CNN.  Regardless of the outcome of that debate, however, the fact is that an uniao poliafetiva is an uniao poliafetiva, not a civil marriage.  Polygamous marriage remains illegal in Brazil.

Same-sex couples have been marrying in Massachusetts since May 17, 2004 and in eight other U.S. states and the District of Columbia for varying periods of time since then.  Yet polygamous marriage remains illegal in every state in the union.

The evidence simply does not support Dr. James’s claim that passage of equal marriage laws leads to the subsequent legalization of polygamous marriage.