And that's before mentioning the fact that both airlines involved are based in Ireland, which is equivalent to the Irish Competition Authority attempting to block a merger between BA and BMI.
Id just like to point out that this is not neccesarily fair. The UK competition authority has juristiction over any market place in the UK, including for travel between the Uk and another nation. As such EI and Ryanair have a significant part of the UK-Ireland airline travel market, so they certainly are within their right to investigate to seek to protect UK consumers.
To put this in context, Stena Line only last year bought Norfolkline's Belfast - Birkenhead ferry route. They are a Swedish Company, with a UK branch purchasing another UK concern, itself owned by another Scandinavian company. Stena needed authorisation from both the UK and Irish competition regulators as part of the market served by the route was in the Irish Republic, even though it was technically a domestic UK route.
It can work both ways. It just happens to be that most of the UK-Ireland market is served by Irish airlines.
Dave