Ireland International footballer Eunan O'Kane and his fiancee Laura Lacole are seeking legal recognition of their humanist wedding.
They are being denied rights afforded to religious couples, a court has been told.
A lawyer for Lacole, 27, and 26-year-old said the law in Northern Ireland offered more generous treatment to people of faith.
Under current law, Ms Lacole and Mr O'Kane's planned humanist wedding next month will not be recognised in law. For such recognition they would need to have a separate civil ceremony.
The couple were at Belfast High Court today to challenge the status quo.
Opening the case in front of Mr Justice Adrian Colton, their lawyer Steven McQuitty said all they wanted was the same protection afforded to those of different belief systems.
"Religious people from Pagans to Free Presbyterians and everything in between enjoy a substantial legal privilege under law," he said. "In a sense the State gives its legal blessing to such marriages."
He claimed the law "denies the same privilege to equally valid groups".
Humanism is a non-religious belief system that rejects the concepts of a higher deity or afterlife.
Humanists adhere to a scientific view of the world and believe humans steer their own destiny.
Mr McQuitty said as the law stood in Northern Ireland the couple's wedding on June 22 would be "legally meaningless".
Humanist marriages are legally recognised in the South, and in Scotland, but not in England and Wales.
Mr McQuitty told the court the case was of "huge public interest", highlighting that there were 4,290 humanist weddings in Scotland in 2015, more than those conducted by the Church of Scotland.
Ms Lacole, from Belfast, and Mr O'Kane, from Co Derry, are taking a case against the General Register Office for Northern Ireland and Stormont's Department of Finance.
Northern Ireland's Attorney General John Larkin is also participating in the hearing.
Arriving at court this morning, Ms Lacole said: "We are both humanists so we want to have a wedding ceremony that reflects who we are as people.
"We can't see how you can differentiate between any types of beliefs. We think it should be recognised in Northern Ireland because there is a need for it. Whether we are a minority or a majority we should still be given equal rights."
She added: "We hope that we get a good verdict which means that we can have the wedding ceremony that we want to have.
"If we don't get it, we want to appeal so we can give other people the opportunity to have the wedding ceremony that they want."
Mr Larkin, who intervened because the case touches on devolved Stormont legislation, argued that humanist elements could be incorporated into a civil ceremony.
"That blunts and weakens the case for a separate ceremony," he told the judge.
He said the applicant had failed to explain what exactly it was they wanted at their ceremony that could not be accommodated in a civil wedding.
"There is a marked paucity of concrete evidence in relation to that," he added.
Philip Henry, representing the General Register Office and Department of Finance, echoed Mr Larkin's assertion.
He said "vows, music, content and venue" could be modified in civil ceremonies, as long as it remained non-religious.
The barrister said the only issue was the couple were unable to have their chosen humanist celebrant to marry them legally.
Mr Henry said the important role religion has played in Northern Ireland through history was why such marriages had become enshrined in law.
"That is not a commentary on the quality of one belief over another," he said.
He made clear the character and motivation of Ms Lacole and Mr O'Kane was not in question, but said any relaxation of marriage laws could "open the door" for less well-intentioned cases in the future that could devalue the institution.
"Where does one draw the line?" he asked.
The barrister added: "If you are looking to protect the dignity and status of marriage it has to be controlled. The less control you have over it the more likely you are to tarnish or devalue it."
He said there was "no prohibition" on humanist weddings, but acknowledged it would be an "inconvenience" to then have a separate civil ceremony.
"An inconvenience does not amount to unlawful interference," he said.
The case continues.