The Northern Ireland First Minister has warned Sinn Fein that any legal challenge to his policy of barring their Ministers from meetings of the North-South Ministerial Council will have little success.
Mr David Trimble made the comments at the publication in Belfast last night of two books by former UUP advisers.
One, The Belfast Agreement - A Practical Legal Analysis, is by Mr Austen Morgan.
Mr Trimble said: "Anybody who is contemplating bringing a legal action connected with the interpretation of the agreement or the Northern Ireland Act with regard to the duties of certain people would be well advised to read Austen's book."
Referring to Sinn Fein's impending challenge to his refusal to nominate that party's Ministers for meetings of the North-South Council, the UUP leader continued: "It's going to be an expensive business for them because these contemplated legal actions are unlikely to succeed."
Mr Trimble also launched a book by Dr Thomas Hennessy entitled The Northern Ireland Peace Process - Ending the Troubles?