With that much at stake, I suggest that several governments put together a large military force and neutralize the Somalian ports that the pirates are based in. That's what the US Navy did once to the Barbary Pirates, and it worked quite well. They stopped bothering American shipping after that. Of course, they actually had a functioning government and chain of command to negotiate with, which the Somalian pirates do not, I gather...nevertheless I think that shutting down and blockading their ports is really the only way to stop them. You have to take the initiative to get control in this sort of situation, not just respond to various separate incidents like a fire brigade.

It would not be necessary to occupy the land in Somalia, and I wouldn't recommend anything of the sort. Just effectively blockade their ports and their seacoast, that's all.