Bea Worton was granted leave to seek a judicial review against the Equality Commission and a local council over the decision to continue to call the park in Newry after Raymond McCreesh.
The 88-year-old’s son Kenneth was one of 10 people massacred by the IRA at Kingsmill, south Amagh in 1976.
In court today her barrister set out how McCreesh was reportedly in possession of a rifle used in the killings when he was captured later that year.
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David Scoffield QC said: “The applicant’s outrage at this decision (in naming the park) is particularly acute.
“She was and remains shocked and bewildered by the insensitivity of the decision.”
Controversy has continued to surround the park since councillors voted to retain the name in February last year.
McCreesh, from Camlough in south Armagh, was one of 10 IRA prisoners who died in the hunger strike in the Maze Prison in 1981.
His convictions included attempted murder, conspiracy to murder, possession of firearms with intent to endanger life and IRA membership.
Proceedings were issued against the Commission and Newry, Mourne and Down District Council.
Part of the case involves a claim that the naming process breached Section 75 of the Northern Ireland Act, which requires public authorities to promote good relations between those of differing religious backgrounds or political opinion.
The Equality Commission, according to Mrs Worton’s legal team, should have found against the local authority and referred the matter to the Secretary of State.
Mr Scoffield accused it of a “volte-face” by switching from an earlier opinion where it had requested the council to review the naming decision.
Tony McGleenan QC, responding for the Commission, argued that it had gone through a painstaking process before making recommendations.
“It’s difficult to establish any arguability that there’s been a public law wrong by the Commission.”
However, Mr Justice Maguire ruled that the challenge should proceed to a full hearing on claims that the Commission was in breach of Section 75 requirements.
He also held that an arguable case had been established against the Council over allegations its decision was irrational, unreasonable, pre-determined or biased.
Rejecting claims the case should be thrown out due to delay, he said: “There’s a matter of public interest involved in this particular decision.”
Mrs Worton, who attended court for the hearing, expressed her delight at the outcome.
“I’m glad the case is going on because that man (McCreesh) wasn’t even from Newry,” she said.
“Why didn’t they name the park after some VIP that really deserved it - I feel sickened that they named it after him.”