User blog comment:DarkSkullPirates/Wano Theories/@comment-1595565-20130125043032

Think of Wano like Cuba and the World Government like the United States. It's possible to go there, but you're on your own once you get there, and are left to your own devices when you want to leave. Basically, in a legal sense, the Straw Hats would have to catch a connecting flight in Ocean Mexico to get to Wano. Not that difficult. However, anyone going there on strict World Government business would get turned away. So, Ace, seeing himself as capable of being on his own and not part of the World Government, was able to go to Wano. Nothing special, nothing to it.