A landmark legal challenge to Northern Ireland's ban on same-sex marriage is to open today. Two couples have been granted permission to judicially review Stormont Assembly's repeated refusal to legislate for same sex marriage. Grainne Close and Shannon Sickles, and Chris and Henry Flanagan-Kanem were the first and second UK couples to enter into a civil partnership, when Northern Ireland became the first place in the UK to make it an option in 2005. [caption id="attachment_267845" align="alignnone" width="594"] Grainne Close and Shannon Sickles having become first UK couple to enter into civil partnership. [/caption] Following the May referendum which saw same-sex civil marriage legislated into law, Northern Ireland remains the only place in both Ireland and the UK where civil marriage is denied to gay couples. Amnesty International has described today's case as "hugely significant". Speaking to RTE,  Amnesty's Northern Ireland programme director, said: "Success in this case could have positive implications for thousands of other couples in Northern Ireland. "Following the repeated failure of the Northern Ireland Assembly to legislate for marriage equality, couples have been forced into the courtroom to demand equal treatment before the law. "It is unacceptable that they have been obliged to sue the Government in order to have what the rest of society takes for granted - for the State to recognise their right to get married."