Are those on cargo ships allowed to carry weapons?

Because it would certainly cut down on the amount of pirates if you could just shoot them before they get on board.Are those on cargo ships allowed to carry weapons?
The company below does maritime security for yachts and merchant ships. According to them whether merchant ships can have guns on them or not depens on the flag of the country the ships is sailing under and also the rules of the countrie that the ship is making port of calls to. There are also cases where a ship may have a very volatile or environmentaly dangerous cargo, which would make it a bad idea to get in a gun fight with pirates. In the majority of cases though ships usually are able to out run or out maneuver the pirates or chase them off with fire hoses or other means. Usually you don't hear about this in the new because its not quite as interesting.Are those on cargo ships allowed to carry weapons?
No they are not thanks to the U.N. A good example of if you ban guns , only the criminals will have them. If the crews of these ships were armed, there would be no such things as Pirates.
The crew and the ship's are unarmed. No cannons like the old days. There are some new passive weapons being invented like loud sound generators, and other things.
no they cant carry guns into other countries but im sure they could drop something heavy or just steer into them or cut their climbing rope