It is already illegal under Section 98 of the Postal and Telecommunications Services Act, 1983, as amended by Section 13 of the Interception of Postal Packets and Telecommunications Messages (Regulations) Act, 1993, for anyone to intercept, without the consent of one of the parties involved and subject to the exceptions provided for in those Acts, telephone calls being transmitted over the public telecommunications system.
Offenders are liable on summary conviction to a maximum fine of £800 and or a maximum of 12 months imprisonment or, on conviction on indictment, a fine of up to £50,000 and or imprisonment for up to five years. I am aware that, with equipment currently available on the market, there is the possibility of listening to conversations on the analogue (088) mobile system and while the practice is illegal, it is very difficult to detect. GSM (087) conversations cannot be intercepted with the same ease.
If the Deputy has a particular case in mind, I would be interested in hearing about it but it may ultimately be a matter for the Garda.