The country's longest serving detective is challenging the law that requires him to retire at the age of 60.
Assistant Commissioner, Martin Donnellan, a Scott medal winner in charge of eight garda units, will be 60 on 7 June.
He says the legislation requiring Assistant Commissioners to retire at that age is irrational, unreasonable and discriminatory.
Mr Donnellan joined the gardaí in 1968 and is the country's longest-serving and most experienced detective.
In 2005, he was appointed as one of 12 Assistant Commissioners and since last year he has been in charge of eight garda units, including The Criminal Assets Bureau, the Drugs Unit, the Bureau of Criminal Investigation and the Immigration Bureau.
Mr Donnellan wants to stay in the force but under legislation brought in 1996 he must retire.
He told the High Court he was extremely disappointed that this issue had not been dealt with before now.
He said he found his current role very interesting and challenging and he said he was not taking this action for money.
Mr Donnellan said the most important attribute for any police officer was experience and if you are doing the job to the optimum, it does not make any difference how long you are in the job for.
The State argues that allowing the Assistant Commissioners to stay on until 65 would block promotional opportunities in a force of almost 14,000 gardaí.
