45 year old Thomas Ash Mellon, Rathmore Road, 34 year old William McDonnell, of Balbane Pass and 51 year old Jason Lee Anna Ceulemans, from Long Tower Court, were found guilty and fined £300 each.
Mellon is believed by police to be the leader of the New IRA in Derry.
Detective Chief Inspector Andy Hamlin said: “All convicted terrorists are required to adhere to requirements set out in the Counter Terrorism Act 2008.
“Detectives from the Terrorist Investigation Unit continue to actively investigate those who breach these requirements and bring them before the courts.”
In 2015, McDonnell and Mellon were jailed for a total of 40 months for having a handwritten note which they attempted to smuggle into the dissident republican wing of Maghaberry prison.
In 2014, Ceulemans was jailed for ten years after he pleaded guilty to a charge of possessing an explosive device to enable some other person to endanger life or cause serious injury to property.
He was one of three men stopped two years earlier by police in the city with an armour piercing bomb in a car.
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