Laura Lee was granted leave to seek a judicial review of Stormont legislation making it illegal for men to pay for prostitutes.
A judge ruled she has established an arguable case that amendments to the Human Trafficking and Exploitation Act breach her human rights to privacy and freedom from discrimination.
A date for a full hearing of the unprecedented legal action will be set later this year.
Northern Ireland is currently the only UK region to make the purchase of sex a criminal offence.
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The legislative change was introduced last year in a private member’s bill brought before the Assembly by Democratic Unionist peer and Stormont MLA Lord Morrow.
Although it shifts the legal burden away from prostitutes, they believe it will put them at heightened risk from customers using fake names to avoid identification.
Ms Lee, a 38-year-old Dublin-born law graduate, has been a sex worker for two decades. She now operates in Scotland, Northern Ireland and the Irish Republic.
Her legal team argued that the new law exposes prostitutes to greater risk of violence.
They contended that it will lead to sex workers increasingly carrying out their business alone, without the protection offered by brothel arrangements.
Reduced opportunities to meet and screen clients creates a further danger, it was claimed.
The court heard Ms Lee was herself exposed to significant verbal abuse during one encounter.
She feared for her own safety but was able to avoid any violence.
Her legal challenge is directed against the Department of Justice - even though former Minister David Ford opposed the new legislative clause.
However, Attorney General John Larkin QC, representing the First and Deputy First Ministers, claimed proceedings should be thrown out at the first stage
He insisted no unlawful act had been identified, and suggested the Act brought in by Lord Morrow provided Ms Lee with greater protection from any abusive behaviour.
Mr Larkin also submitted that protections under the European Convention on Human Rights do not cover sex for hire.
Ruling on the application for leave to seek a judicial review, Mr Justice Maguire acknowledged the Attorney General’s points had “considerable force”.
But he held that the arguments advanced by Ms Lee’s legal team were strong enough to meet the “modest threshold” of securing the right to progress their case.
The judge stressed his verdict was no indication that she will ultimately succeed.
Outside court Ms Lee’s solicitor, Ciaran Moynagh, backed the decision.
He said: “We need scrutiny on the legislation surrounding sex work in Northern Ireland to ensure the human rights of all are protected, and sex workers are not put at greater risk as a result of the laws.
“It’s not satisfactory that human trafficking and sex work is conflated as this leads to ineffective policy and law.”
Meanwhile, a group calling itself SPACE (Survivors of Prostitution-Abuse Calling for Enlightenment) said today that the law Ms Lee is challenging in fact serves to “protect the human rights of people who are abused and exploited in prostitution”.
SPACE Executive Director Rachel Moran, who gave evidence to MLAs at Stormont in support of the law, said: “As a group of survivors of prostitution we strongly oppose this challenge. We know, through the experiences of our own lives, that prostitution is a damaging, dehumanising and demeaning system of exploitation. We will do all we can to oppose this misguided challenge.”
SPACE UK Representative Fiona Broadfoot added: “If Section 15 [the sex buyer law] was reversed it would send the message to traffickers and pimps that they can do business again in Northern Ireland, which would put more women at risk. This Act serves to protect the most vulnerable women and children in society and we want to see that legacy continue. It is extremely selfish of Laura Lee to try to overturn this law for the sake of her own financial stake in the issue.”