Yeah, "supposedly" so are Hancock, Moria and Crocodile.
I think we've yet to see a Shichubuki who was actually loyal to the World Government. They're all either secretly betraying the WG like Moria and Crocodile, or they're sparing pirates that they should be capturing like Kuma and Hawkeye.
Also, as far as Perona is concerned, he may not have had the authority to arrest her. She was part of a Shichubuki's crew, not a pirate crew.