The family of murdered GAA official Sean Brown has said they are "devastated” the government has rejected a coroner’s request for a public inquiry.
In a statement issued by their solicitor, they said they will mount a legal challenge.
Mr Brown, 61, was shot dead near Randalstown in County Antrim in 1997 after being abducted by loyalists.
In February, it emerged that more than 25 people, including state agents, were linked by intelligence to the murder.
What happened to Sean Brown?
Mr Brown was locking the gates of GAA club Bellaghy Wolfe Tones when he was taken by the Loyalist Volunteer Force (LVF).
In March, the coroner said Mr Brown's inquest could not continue due to material being withheld on the grounds of national security.
He decided that redactions of intelligence material meant he could not properly investigate the circumstances of the killing.
Instead, he wrote to Northern Ireland Secretary Chris Heaton-Harris, requesting a public inquiry into the case.