Aer Lingus has launched a High Court challenge against a ruling by the Irish Takeover Panel that could allow Ryanair make another bid for the national carrier in August.
The action arises out of Ryanair's failed €694m bid to win control of Aer Lingus.
That offer, which was Ryanair's third bid for its rival, was formally tabled in late July 2012.
Last February the bid was blocked by the EU Commission.
The commission said the proposed merger would harm consumers by creating a dominant company on 46 routes where the carriers are currently competing.
Last week, the Irish Takeover Panel ruled that if Ryanair decides to make another offer for Aer Lingus, it must wait until August of this year - some 12 months after the bid was first tabled.
The panel is the body responsible for monitoring and supervising takeovers and other relevant transactions in companies in Ireland.
It prohibits bidders from making a further offer for a public company within a year of the date on which their original offer has lapsed.
Aer Lingus disputes that ruling.
It says that the 12-month period starts from February when the EU Commission decided to block Ryanair's offer.
Today when the matter was briefly mentioned before the High Court Paul Sreenan SC, for Aer Lingus, said it was Aer Lingus's intention to seek to have the takeover panel's decision judicially reviewed.
It was Aer Lingus's case that Ryanair cannot make another bid to take over Aer Lingus until February of next year at the earliest.
Counsel added that the takeover panel's decision was "wrong in law", adding that they are seeking an order from the court quashing the panel's decision.
Ryanair and its subsidiary Coinside Ltd, through which the bid for Aer Lingus was made, are notice parties to the action.
Mr Justice John Cooke noted Aer Lingus's intention to seek permission to bring judicial review proceedings and adjourned the matter to 10 June.
Ryanair's offer was its third attempt to take over Aer Lingus. The Government, which holds a 25% stake in Aer Lingus, opposed the takeover bid.
Ryanair, Aer Lingus's biggest shareholder with a 30% stake, first tried to take over Aer Lingus in 2006 but was blocked by the EU Commission.
Ryanair dropped its second bid in 2009.