A Stormont department unlawfully stopped a convicted murderer continuing to work as a groundskeeper, the High Court heard.
Lawyers for west Belfast man Martin Neeson claimed he was wrongly and irrationally deemed unsuitable for a job he had carried out for 18 years after release from prison.
They argued that the move was based on an earlier decision taken by Peter Robinson during his tenure as Finance Minister back in 2007 that should have gone before the full Executive.
Neeson's judicial review challenge centres on an alleged failure to continue with guidance for employers on recruiting staff with conflict-related convictions.
Described as a former political prisoner, he got out of jail in 1987 after serving eleven-and-a-half years for a murder committed when he was aged 16.
No further details of the killing four decades ago were disclosed in court.
Following his release he secured groundskeeper work with a conservation charity in the Poleglass area of Belfast.
But due to a technical change in the body's contractual relationship with the civil service he had to undergo security vetting.
Checks carried out by Access NI resulted in the Department of Finance and Personnel deciding in December 2014 that he is unsuitable to continue in the role.
Neeson went to Sinn Fein to seek their help in lobbying on his behalf.
But after that proved unsuccessful he issued proceedings against the department.
In court on Wednesday, a judge was told the guidance had been formulated as part of the Good Friday and St Andrew's political agreements.
Barry Macdonald QC, for Neeson, said it was adopted by the Office of the First Minister and Deputy First Minister (OFMDFM) before Mr Robinson decided it should not apply.
The barrister argued that under Stormont rules the then Finance Minister should have taken the issue to the Executive because it was significant, controversial and cut across departments.
He told the court Sir Nigel Hamilton, a former head of the Northern Ireland Civil Service, appeared to be unaware the guidance had been revoked when he gave evidence to the Finance and Personnel Committee in 2012.
"It remains incongruous for these guidelines not to apply to the Civil Service in circumstances here OFMDFM adopted them and recommended to everyone else they should apply," Mr Macdonald said.
"It was prima facie unlawful for the Minister of Finance and Personnel to disapply the guidance.
"If it had been in force the applicant would not have been deemed unsuitable for this particular job."
The hearing continues.
Outside court Neeson's solicitor said the decision had resulted in him losing employment he had performed "diligently" for 18 years.
Niall Murphy of KRW Law added: "The intention of these proceedings is to render that decision unlawful and irrational, which will lead to Mr Neeson resuming his job."