Yo-ho, yo-ho, it's a pirate-hunter's life for me!
Gimme an M-60 or an M-203 and I'm good to go. Where do I sign up?
Problems with huntin' pirates:
1. Gub'mints don't approve other folks usin' force. They like to think of themselves as sole legitimate users of force. Otherwise, freighters and cruise ships headed for "iffy" locations would have a decent armament for self-defense and insurance companies would reward 'em for it.
2. Pirates have nothin' worth taking and nobody is payin' for their extermination.