With any luck they'll soon annexe their own territory and set up a sovereign state of their own. Once that happens those countries that are patrolling the seaways, trying to stop the pirates can issue an ultimatum to the new government - stop these acts of aggression or we'll take steps to stop you. The pirate raids would continue.
Shortly afterwards we could commence some aggression of our own. A clutch of pinpoint bombing raids, followed by a land offensive, and we'll have the job done inside a month.