CHICAGO(AFP) - A dying gay man has won the right for his husband to be buried next to him after a US federal judge ruled Ohio's refusal to recognise same-sex marriage is unconstitutional.

The ruling offers hope to gay rights activists that similar state bans can be successfully challenged and comes a month the US Supreme Court struck down a law denying federal benefits to homosexual couples.

John Arthur was diagnosed with Lou Gehrig's Disease in 2011 and is currently in hospice care for the fatal disease, which results in severe muscle deterioration.

Earlier this month, friends and family helped pay for a medically-equipped jet so Mr Arthur and his partner of 20 years, Mr James Obergefell, could be joined together in a state that recognises gay marriage.

They were married on July 11 on the tarmac of a Maryland airport and flew home to Cincinatti the same day.

The couple wishes to be buried together in Mr Arthur's family plot, but the cemetery only allows descendents and married spouses to be interred together.

So they asked a federal court for an injunction to require the state of Ohio to list Mr Obergefell as Mr Arthur's spouse on his death certificate.

"This is not a complicated case," Judge Timothy Black wrote in the ruling issued Monday. "Throughout Ohio's history, Ohio law has been clear: a marriage solemnised outside of Ohio is valid in Ohio if it is valid where solemnised."

Judge Black ruled that the state's ban on gay marriage violates constitutional guarantees of equal protection under the law.

The judge ordered the local registrar of death "not to accept for recording a death certificate for John Arthur that does not record Mr Arthur's status at death as 'married' and James Obergefell as his 'surviving spouse'." Ohio has not yet announced whether it will appeal the ruling.

The Supreme Court's landmark decision in June required the federal government to recognise gay marriages obtained in the 13 US states that have legalised the practice.

However, gay marriage advocates were hoping it could be used to challenge bans on gay marriage in 35 other states.

"Indeed, just as Justice (Anthony) Scalia predicted in his animated dissent, by virtue of the present lawsuit 'the state-law shoe' has now dropped in Ohio," Judge Black wrote in his 15-page ruling.