The coast guard has medium machine guns and .50 cal sniper rifles to disable ships (small ones), i would say that's fairly on the lines with what is needed, the civilian ships need this too, ports also need to be defended. And not enough defence as to stop a invasion, just enough to stop 4-6 ships full of punk asse's with ak-s and Rpg's.
The problem is also each ship taken and captured further increases the weath and (reason) for new pirates to pick up a gun, grab a boat and try to high jack someones ship. Its becoming popular again...how much would you like to bet the average person is more concerned about the raids incoming $ for ransoms and what they can do with the $, than they are about learning to read or wright. You all saw the report's of the happy villagers and shop owners praising the pirates for the recent money influx. The mother of one of the pirates killed recently condeming america for her sons death and claming her son is fighting for they're nation & people, and for there shiping lanes, fish. So lady,your son went out to fish with ak-47's & Rpg's and came back with 30 hostages a huge ship & a few million in food, sent to other starving nations in international waters. I suppose the term fishing is different to you and your people then it is for the rest of the world.
Difference between a Pirate, High Jacker & Terrorest? Absolutely nothing, only motive and the end resolve.