Ryanair is entitled to sue in this jurisdiction over alleged "screen-scraping" of its booking website by two travel agencies based in Germany and England, the Supreme Court ruled.
Screen-scraping, Ryanair says, involves the taking of information from its website and providing it to the travel agencies’ customers for a fee.
Those actions are still pending.
Both travel agencies argue a customer is not purchasing flight tickets from them but is simply forwarded to the Ryanair site.
In preliminary cases over where the airline could bring its action, the travel agencies argued they should be in their respective home jurisdictions. Ryanair disputed this.
Delivering a unanimous judgment on Thursday on behalf of a five-judge Supreme Court, Mr Justice Peter Charleton upheld two separate High Court judgments in favour of Ryanair on the question of jurisdiction.
The two travel agencies, Billigfluege.de GmbH/Ticket Point Reiseburo GmbH, based in Germany, and On the Beach, based in England, had appealed separate rulings that Ryanair could sue them here.
Mr Justice Charleton said the case centred on what is commonly known as the “Brussels I Regulation” of 2000 on jurisdiction and enforcement of judgments in civil and commercial cases in EU member states.
At issue was the use by the online travel companies of Ryanair’s website to book flights for their customers instead of the customers directly accessing the airline’s own website.
The result for the customer is a slightly higher price but with a choice of several airlines flying from one destination to another, Mr Justice Charleton said.
In separate cases before the High Court, judges rejected the travel agencies’ arguments they should be sued in their own countries in relation to the dispute.
Mr Justice Charleton said in both cases a consensus emerged as to jurisdiction in favour of the courts of Ireland and both appeals by the travel agencies should be dismissed.
The Brussels I regulation states a person domiciled in a member EU state should be sued in the courts of that state, he said. Exceptions can occur where there is agreement between the parties.
There had been no demonstration of error in the High Court decisions which were in accordance with Irish and EU precedent on the application of the Brussels I regulation, Mr Justice Charleton said.