Section 99 (2) of the Postal and Telecommunications Services Act, 1983 provides a person who connects or causes to be connected any apparatus or device to, or places or causes to be placed any apparatus or device in association or conjunction with, the telecommunications system operated by the company or any part of the system the effect of which might result in the provision by the company of a service to any person without payment of the appropriate rental, fee or charge shall be guilty of an offence.
Summary proceedings for such an offence may be brought by Telecom Éireann.
Whether or not any decoding or reregistering operation is illegal would be a matter for a court to decide.