A lesbian couple from North Yorkshire who were married in Canada have pleaded with a High Court judge to give their union full legal status in the UK.
The couple say their human rights are being breached
University professors Sue Wilkinson and Celia Kitzinger said new UK laws which validated their union as a "civil partnership" were not good enough.
The University of York and Loughborough University academics were declared "wife and wife" in a 2003 ceremony.
Their case for "declaration of validity of marriage" is due to last four days.
'Insulting and discriminatory'
They have argued that if a heterosexual couple got married in Canada and then returned to England their marriage would be automatically recognised and registered.
The Civil Partnership Act, introduced last December, gave gay partners in the UK many of the rights enjoyed by married heterosexuals.
But the act states that same-sex couples who marry in countries where such marriages are lawful "are to be treated as having formed a civil partnership".
The couple, who have been together for 16 years, said it was "insulting and discriminatory" to be offered civil partnership instead of marriage.
In a statement read to the High Court, Ms Wilkinson said: "It is important to both of us that we are recognised as partners in life by the world at large."
'Laws of exclusion'
Karon Monaghan, representing her, said laws prohibiting marriage between different social classes or religions had long been repealed but there were still laws banning same sex partners from marrying.
If the factors preventing the marriage being recognised were because the couple were black or of mixed race, "it will be very clear that such laws are repugnant", she said.
"There is no real difference between such laws of exclusion.
"Having regard to the Human Rights Act, such laws cannot survive."