It comes as Ms Smith, who went to Syria during the civil war, won a legal challenge against a ruling banning her from Northern Ireland.
Currently charged with membership of IS, Ms Smith appeared remotely in front of the Special Immigration Appeals Commission (Siac) in London last month, to challenge a Home Office ban on her crossing the border.
The Home Office say they are considering appealing a ruling in favour of Ms Smith.
In response to the ruling, the Home Office said: “We are disappointed with this judgment and are considering our options for appeal.”
Meanwhile, Ulster Unionist peer Lord Empey said the Co Louth woman should be arrested if she enters the North.
“If she sets foot in Northern Ireland – or any other part of the United Kingdom for that matter – she must be immediately arrested so the UK authorities can question her and establish whether or not she was involved in Isis terrorist activity that impacted on UK citizens,” he said.
While she is from Dundalk, Ms Smith’s father and much of her family are from Belfast.
As such, she argued she was entitled to hold a British passport and should be allowed to travel freely within the UK, including to visit her family.
Her defence argued it is discriminatory under the European Convention on Human Rights to treat children of unmarried parents any differently to those of married couples. Delivering the ruling yesterday, Siac accepted the Home Office ban was discriminatory.
Ms Smith’s solicitor Darragh Mackin of Phoenix Law welcomed the ruling.
“The decision to exclude our client was discriminatory and contrary to the basic principles underpinning the Good Friday Agreement,” he said.
“As an Irish citizen who resides in a border town, it was always asserted that to restrict her from travelling across the border was unlawful and could not be stood over.
“We warmly welcome the court’s determination today, which will reinstate our client’s basic rights to travel to the north of Ireland at her convenience.”
Speaking to the Belfast Telegraph last month, Ms Smith said she had, “close family ties to the North and, as a result of unproven allegations against me, I have been unfairly excluded from the north of Ireland”.
“I have, therefore, instructed my solicitors to robustly challenge this exclusion on the basis that it is contrary to my rights and contrary to the Good Friday Agreement,” she explained.
The former soldier, who converted to Islam more than a decade ago, travelled to Syria in 2015 to live in IS’s self-declared caliphate.
She married and had a child with British jihadist Sajid Aslam, who is thought to have died in the conflict. On December 31, 2019, Ms Smith was issued with an order banning her from the UK.
The Home Office argued that because her parents were not married at the time of her birth, she did not qualify for automatic citizenship.
The case is similar in nature to that of Shamima Begum, the east London woman who left England to live in Syria when she was 15 and has since been stripped of her UK citizenship.
Mr Mackin argued UK Home Secretary Priti Patel failed to take into consideration the dual nationality of those with northern parentage, as enshrined in the 1998 Belfast Agreement.
Her defence also argued that at the time of her birth, in February 1982, the British Nationality Act provided for automatic conferral of British citizenship on children born to a UK father.