Supporters of equal marriage in the US state of Tennessee have said they are encouraged by a federal judge’s ruling that Oklahoma’s same-sex marriage ban was unconstitutional.

A lawsuit, filed by the National Center for Lesbian Rights, in October, challenges Tennessee’s ban on equal marriage.

Filed on behalf of two lesbian couples and two gay couples, all married out of state, the lawsuit seeks to challenge both the state law banning equal marriage, and the constitutional provision which stops the state from being able to recognise same-sex marriages.

Despite that a Tennessee judge in a same-sex marriage lawsuit is not now required to rule in the same way, advocates of equal marriage are hopeful that it may prove influential.

Attorneys acting on behalf of the plaintiffs said that people across the country are in favour of same-sex marriage, not just those in more Democratic-leaning states.

The constitution in the state of Tennessee defines marriage specifically as between one man and one woman.

US District Judge Terrence Kern ruled that Oklahoma’s ban on same-sex couples marrying violated the US Constitution. A similar ruling was made in Utah several weeks ago. Both rulings are subject to a stay, pending appeal.

The attorney general’s office in Tennessee has issued a statement saying, “Nothing in these two cases changes our position that Tennessee’s laws are constitutional.”

A spokesman for Governor Bill Haslam Dave Smith said: “The law is clear here. Those decisions don’t affect Tennessee.”