The man was arrested by the PSNI's Serious Crime Branch
A 23-year-old man is being questioned about riotous behaviour following a parade in Lurgan, County Armagh, last month.
He was arrested by detectives from the PSNI's Serious Crime Branch on suspicion of possessing petrol bombs.
Police said the arrest was in relation to an "illegal parade" in Lurgan on 23 January.
The republican parade, which began in the town's Kilwilkie estate, was in support of prisoner Martin Corey.
Last year, the NI secretary of state revoked the licence of Mr Corey, who was jailed in December 1973 for the murder of two policemen.
He had previously been released on licence in June 1992.
