Why are'nt such ships allowed to arm themselves?
Wish they could. That would fix the problem over night. A couple dead pirates would cause the rest to find some other crime.
Problem is that these ships travel in international waters that all have different laws prohibiting armed sailors. I think most people in the U.S.A. would be a bit nervous seeing a cargo ship trying to sail in U.S. waters with armed Arab sailors because the ship left Yemen with it's cargo and had to cross pirate infested waters to get here.
This would also be a problem for civilian sailors with home ports in Britain or Australia because their governments will not allow people to own guns on dry land let alone out on the open seas.
Anybody remember one of the the around the world attempts to circumnavigate the globe with a hot air balloon by ( I think ) Steve Fossett ? He almost had to abort because some country ( I think Egypt ) had not given permission to cross their airspace ? I think he got permission at the last minute or the winds changed or something. Like a hot air balloon at some insane altitude is a threat or hazard - NOT.
However , where there is a problem , there is opportunity.
I suggest this ~
Get some Blackwater guys or Spec Ops retirees and let them become mercs for hire. Have them based in the Gulf of Arden and when entering the area pick up a group , travel through the gulf , Have someone pick them up at the other side for a trip going the other way .
Could be a rather profitable gig , with a great side affect - DEAD PIRATES.
There is no law or government currently in the area which makes this much easier to implement , Plus dead pirates make others quit.