From encyclocentral (http://globaleconomicanalysis.blogspot.com/2008/11/second-push-to-stop-auto-bailout.html):

Crime against international law are basically those crimes that are defined by treaty and are comprised of crimes of apartheid, crime against peaces, crimes related to war, piracy, genocide, trading of slave as well as starting a war of aggression. The prosecution is carried out by the application of extraordinary ways mostly by the courts
working internationally like the International Criminal Court that is located at The Hague in the Netherlands.

Here's an even better source (http://war-crimes.suite101.com/article.cfm/piracy_forced_creation_of_universal_jurisdiction):

Jurists and political analysts on the other side of the discussion contend that the principle of universal jurisdiction evolved out of a need for all states to regulate certain behavior and address crimes that affected all states. For them, this evolution began with piracy and progressed until it entered the arena of war crimes, genocide, and crimes against humanity.

So you see, the International Criminal Court is the perfect arena for trying pirates, both historically and currently.