Ryanair has initiated legal proceedings against the Taoiseach and the State over travel restrictions and the 'green list' of countries deemed safe to travel to.
The airline, whose business has been hugely damaged this year, is asking the High Court for a judicial review of restrictions arising out of the Covid-19 pandemic.
It claims these are unlawful, amount to a disproportionate interference with an individual's rights and are detrimental to its business.
The green list, announced on July 22, contains just 15 countries and does not include the UK, Germany, France or Spain, all of which are major destinations on Ryanair's network.
The proceedings, which were widely expected, were initiated against the Taoiseach, Ireland and the Attorney General. Aer Lingus Ltd is a notice party.
Lawyers for Ryanair went before Mr Justice Charles Meenan yesterday, but he directed the airline bring its application for leave on notice to the defendants so they can be represented in court.
The judge said given the urgency of the case, it may be possible to have "a telescoped hearing" where both the application for leave and the challenge itself are heard at the same time.
In correspondence opened to the court, the State strongly denies the measures challenged were unlawful.
It said they were advisory and not mandatory in nature and there was no basis for a legal challenge. The State said its Covid-19 travel advisory notices in relation to non-essential travel were necessary, proportionate and transparent measures designed to deal with the global health emergency.
It said that the green list of countries would be reviewed on a fortnightly basis based on advice from public health officials.
But Martin Hayden SC for Ryanair said the restrictions were more than just advice.
He agreed with the judge that its case was essentially that the Government had introduced what were effectively "mandatory" regulations "under the cloak of advices".
The restrictions represented law making by the executive which ought to have been made by the Oireachtas, counsel said.
Ryanair has argued the green list was not provided for in legislation and has been put in place by the Government by way of public announcement, on a non-statutory basis.
It says that consequently, the Oireachtas was being denied the opportunity to consider the travel restrictions, and these have not been subjected to the democratic scrutiny, or the safeguards, checks and balances they should have been.
In a submission to the Special Committee on Covid-19 Response earlier this week, Ryanair claimed Ireland's policy on foreign travel was unjustified and completely disproportionate to the risks involved.