Up to 30 people staged a protest outside a police station where a senior member of the Progressive Unionist Party is being questioned.
A group of protesters gathered outside Antrim police station
Billy Hutchinson, a former assembly member, is one of seven people arrested by police investigating the murder of north Belfast schoolboy Thomas Devlin.
Thomas, 15, was stabbed close to his home in August 2005. Police believe his killers are from the Mount Vernon area.
PUP leader Dawn Purvis said she was "angry" about Mr Hutchinson's arrest.
"We all want to see the killers of Thomas brought to justice, that's without question, it was a despicable murder," she said.
Billy Hutchinson is among those being questioned
"But I do have to question the arrest of Billy Hutchinson. If police wanted to talk to Billy about comments he made, why did they not go to Mount Vernon Community House and speak to Billy there?"
A group of protestors gathered outside Antrim police station, where the seven are being questioned. That protest has now ended.
No one has ever been charged with Thomas Devlin's murder.
Mr Hutchinson is a former assembly member for the Progressive Unionist Party, the political representatives of the Ulster Volunteer Force.
Now a community worker, he is also a former UVF prisoner who played a key role in the organisation's announcement earlier this year that it was standing down.
He also joined a senior UVF delegation in talks with General John de Chastelain, the head of the decommissioning body.