Ireland's highest appellate court has rejected a bid by the founder of the Real IRA paramilitary group to have his 2003 conviction for "directing terror" overturned.

Lawyers for Michael McKevitt had argued that the 63-year-old should be freed from prison because the warrant used to search his home was illegal, and because McKevitt himself fired his lawyers midway through his original trial.

But the three-judge court ruled Friday that McKevitt's complaint was "unstateable and unarguable."

McKevitt received a 20-year prison sentence chiefly based on testimony from an American spy who passed information to British and U.S. law enforcement agents.

The Real IRA opposes Northern Ireland's 1998 peace settlement. That year the group killed 29 people with a car bomb in Omagh, the deadliest blast of the entire conflict.