A student who was refused a place in the Army Cadet School after a change in the entry rules has won a High Court action and can begin his course immediately.

Gavin Morrissey, aged 19, had challenged changes introduced last April for admission to the course which prevented him from using the results from two Leaving Cert exams.

In his proceedings, Mr Morrissey, from Airmount Road, Slieve Rua, Co Kilkenny, claimed a material change last April in entry requirements prevented him starting the course this year and meant he could not do so unless he sits the Leaving Certificate a third time.

Mr Justice Michael McGrath ruled that the Minister for Defence, "perhaps unwittingly and perhaps unaware of the impact on Mr Morrissey", had promulgated terms which had the effect of "changing the goalposts after the game had begun".

Following the decision, Patrick Leonard SC, for the Minister for Defence, said Mr Morrissey could start the course today.

Outside court, Mr Morrissey said he was "very relieved" but did not wish to comment further.

The dispute concerned whether Mr Morrissey, who sat and passed the Leaving Cert in 2017, and again in 2018, was entitled to 'carry forward' a pass in Maths in the 2017 exam to meet the requirement of achieving passing grades in six higher or ordinary level subjects.

Mr Morrissey says he only learned, from a Defence Forces email of June 2018, of the Minister's decision of 29 March 2018 to prevent results being carried forward from one Leaving Cert to another. That decision was set out in terms and conditions published on 1 April 2018 on the Defence Forces website.

The June email also set out the terms and conditions for cadet school admissions and noted all the minimum educational requirements must be met in a single sitting of the Leaving Cert.

Mr Morrissey said the first maths paper of the Leaving Cert was over when he got the email.

His counsel Oisin Quinn said there was no dispute the Minster was entitled to change the rules for admission. His case was there should be clear and adequate notice of those to affected persons like Mr Morrissey.

Outlining his decision today, Mr Justice McGrath said there was no dispute the Minister is entitled to set terms and conditions related to minimum educational requirements.

The issue was the legality of how the terms and conditions were altered without notice to Mr Morrissey and how they were applied to him.

The judge found, while the Minister was entitled to make changes, it was unfair and legally unreasonable for him to make such a change in such a period of time.

The judge accepted Mr Morrissey had relied on how the rules operated over previous years.

It appeared some sections of the Defence Forces also shared Mr Morrissey's understanding of the rules, he noted.

The changes were published on 1 April 2018, two months before the Leaving Certificate exams were due to start, he said. Even if Mr Morrissey had read them then, he had already dropped maths and had no real opportunity to address the changes.

The fact Mr Morrissey's parents incurred €6,000 expenses by his resitting the Leaving to meet the requirements as he understood them, and the fact he dropped Maths, all showed as a matter of probability he relied on the previous rules.

Mr Morrissey had a legitimate expectation the rules would not change as they applied to him without "some reasonable forewarning".

It was unreasonable and contrary to his legitimate expectation that, at a minimum, the entry requirements would not be changed in such a way without "clear notice".

The judge adjourned the matter to 13 November and said his full judgment will be available later.