BELFAST — Northern Ireland’s power-sharing government will soon face a human rights legal case over its refusal to allow gay couples to marry, warns Amnesty International and local LGBT rights organization the Rainbow Project.

Last year, lawmakers voted to make Northern Ireland the only part of the United Kingdom where LGBT people are excluded from the United Kingdom’s proposed marriage equality, which was passed in the House of Commons in February.

Spokesperson for the groups say “it is inevitable that the LGBT community will use the Human Rights Act and European human rights legislation to force Northern Ireland to bring the law into line with Britain,” reported The Guardian.

Legal proceedings will likely be tried in Belfast, which, ironically, was the first city in the UK to host a gay civil union in 2005.

Patrick Corrigan, Amnesty’s program director in Northern Ireland, said states can not discriminate against same sex couples in different parts of its territory.

“That obligation is clear in international law. This means marriage should be available to same sex couples in Northern Ireland just as soon as it will be to couples in other parts of the UK,” he said.

The Rainbow Project said excluding Northern Ireland from gay marriage law meant that if a married LGBT couple from England relocated there due to work or family reasons, their marriage would in effect be null and void.

As late as 1982 gay sex was still a criminal activity in Northern Ireland because the country was not included in the UK’s gay law reforms of the 1960s.

Gay rights campaigner Jeff Dudgeon took a case to the European court of human rights in 1981 which forced the UK government, in the face of opposition from unionist politicians such as the Rev Ian Paisley, to decriminalize homosexuality in Northern Ireland.